1,721,410 research outputs found
Damage resistance and damage tolerance of thin composite facesheet honeycomb panels
Full text linkThesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1989.Includes bibliographical references (leaf 118).by Simon Charles Lie.M.S
Diet composition of Bathyraja interrupta (Gill and Townsend, 1897) and Bathyraja aleutica (Gilbert, 1896), from the northern Gulf of Alaska continental shelf
Full text linkby Simon Charles Brown."A thesis presented to the faculty of Moss Landing Marine Laboratories."Thesis (M.S.) -- California State University, Monterey Bay, 2010."A thesis presented to the faculty of Moss Landing Marine Laboratories.
Le Duc de Biron Colonel du regiment du roy infanterie m'ayant ordonné de quitter le dit Regiment du roy dans le quel j'avois l'honneur d'Etre lieutenant & Cela pour des raisons, de la validité des quelles le public peut juger ... pour Engager le Duc de Biron a me donner vne satisfaction qui selon toute apparence n'est pas de son goust pour ne point Ennuyer le Lecteur je n'entreray que dans vn detail absoluement necessaire ... : [... du 27. May 1742.]
No full textBriefsammlung (Datierungen April und Mai 1742) und Kommenatre des Baron de Tubeuf bezüglich einer Satisfaktionsangelegenheit mit dem Duc de Biron[Simon Charles Baron de Tubeuf]Titel ist TextanfangErscheinungsjahr bestimmt nach Datierung im Tex
Analysis and control of a brushless D.C. motor drive
No full textBrushless dc drives are currently finding widespread application owing to their high performance and low maintenance requirements. However, existing models used in their analysis and control are inappropriate for the prediction of some aspects of dynamics, such as torque ripples. Two models are proposed; the first uses two axis theory and develops an ac type model of the machine; the second uses phase equivalent circuits and a numerical representation of the complete drive system. The first is ideal for permanent magnet synchronous machines, provided that their parameters are accurately known but becomes highly complex when applied to the brushless dc drive. The second has been applied to an all digital brushless dc drive and gives reasonable results although further refinement may be required.Transfer function for permanent magnet synchronous machines, valid for small excursions about a point, have been developed using the two axis model and are compared with results obtained by experiment. The theory accurately predicts the phase response and the shape but not the magnitude of the gain response, for which the theoretical results are overdamped. Torque ripple can be substantial in brushless dc drives but measures to reduce it tend to compromise dynamic response. Two methods are examined: a novel excitation scheme which reduces torque ripple with only a smallreduction in dynamic performance, and the introduction of acceleration limits which achieves large reductions in ripple with a large effect on dynamic performance. However further development of these methods into a dual mode controller which sets acceleration limits according to operating conditions reduces torque ripple to levels which could not be measured using the equipment available.</p
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
The synthesis and characterisation of pyrochlore frameworks
No full textStructural studies have been undertaken on a wide range of pyrochlore phases, with afocus on garnering a better understanding of the factors determining the formation andbehavior of these materials. Extensive structural characterisation has been undertakenprimarily using powder X-ray and powder neutron diffraction techniques to explore thesubtle structural changes that occur as a result of changes in composition on the twointerlocking networks that make up the pyrochlore structure.Particular attention has been paid to hydrated beta-pyrochlore materials, using highresolution TOF and constant wavelength PND to accurately determine the location andorientation of the water molecules within the structure. The location of these moleculeshas been shown to be directly correlated to the overall lattice dimensions of thepyrochlore framework, with the subsequent molecular orientation and internal bondangles changing to provide an optimum stabilization effect on the A-site cation.Investigation into the effects of hydration upon the superconducting beta-pyrochloreseries AOs2O6.nH2O (where A = K, Rb and Cs) has also been investigated; with acorrelation between the structural changes, the degree of hydration and the onset of thesuperconducting state being discussed.Also presented is work seeking to determine the scope and effects of ion-exchange onthe A2O’ network of the pyrochlore framework, with several new phases synthesised andother known phases extensively characterized along with a discussion regarding thelimits of what may be included in the pyrochlore framework
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