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Investigation of the folding of metallothioneinWilson, Christopher John Clifford January 1996 (has links)
No description available.
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The Free Space Radiation Mode method in integrated opticsReed, Martin January 1998 (has links)
No description available.
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Possible dynamic roles for the electrostatic force in biological membrane systemsBerry, Richard M. January 1992 (has links)
No description available.
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Neutron scattering studies of antifluorite compounds at high temperatureFarley, Thomas William Dashwood January 1989 (has links)
No description available.
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Kinematic analysis of foldable structuresFarrugia, Pierre January 2008 (has links)
The main objective of the present research is to develop a general method for the kinematic analysis of foldable structures. This objective is achieved in terms of a method called 'matrix dependency constraint' (MDC method) which is described in this thesis. The MDC method involves algebraic formulation of the geometry, degrees of freedom at the joints and the support conditions of a foldable structure.
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Recycled aggregate concrete (RAC) for structural purposesDi Niro, Gaetano January 1999 (has links)
The possibility of using demolished concrete waste as aggregate in fresh concrete in the production of prestressed concrete beams is checked in this research. As opposed to the use for road foundations or as fill-in material the use of the Recycled Aggregate (RA) for concrete structures requires more tests and processing of results. In fact to be able to use a material for construction it is essential to assess more than just its compressive strength. After the physical and chemical characteristics of the RA and the properties of both the wet and hardened Recycled Aggregate Concrete (RAC) have been determined, it is important to check if the mathematical models and numerical correlation normally used for design of ordinary concrete (such as mix-design procedure, design codes, non-linear analysis) are suitable for RAC. For this reason the main task of this investigations has been to ensure that RAC has satisfactory mechanical performance for structural use and later to guarantee a consistency of the results using methods checked for RAC. A mix-design procedure suitable for RAC to attain the desired workability and the target strength was the first step. Tests on durability of RA and RAC have been performed and the results reported. Finally three 15.0 metres span prestressd beams cast with different percentages of RA (one with 100% of RA, one with 100% of Natural Aggregate NA, and one with 50% of RA and 50% of NA) have been tested. The results show that it is practicable to make prestressed concrete elements using concrete made with Recycled Aggregate and that these elements can have satisfactory and predictable mechanical performance.
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Etude par spectroscopie Raman de la structure des domaines périodiquement polarisés dans le niobate de lithium (PPLN) / Study of the periodically poled lithium niobate (PPLN) domain structure by means of raman spectroscopyHammoum, Rachid 10 June 2008 (has links)
Les investigations des effets non-linéaires (NL) qui apparaissent dans les cristaux ferroélectriques deviennent de plus en plus approfondies, et au temps présent, les cristaux optiques NL deviennent de plus en plus utilisés pour le développement de nouvelles sources de radiations cohérente visibles, conversion de fréquences, ainsi que la détection et diverses transformations de signaux et d images. Un cristal très représentatif de cette classe de matériaux est le niobate de lithium, LiNbO3 (LN), qui depuis son apparition n a cessé de surprendre en révélant de plus en plus ses propriétés. Dans ce travail nous montrons comment la microsonde Raman peut être utilisée pour la caractérisation des microstructures de domaines ferroélectriques dans du niobate de lithium périodiquement polarisé (PPLN). L intensité Raman de modes transverses et longitudinaux de phonons optiques a été enregistrée au travers des stries des domaines ferroélectriques à la surface et en volume d échantillons en z-cut , congruents ou dopés, dont l origine provient de différentes techniques de fabrications. Le changement des intensités intégrées à travers ces structures de domaines a été attribué à une influence des contraintes mécaniques et partiellement du champ de dépolarisation écranté. Nous montrons ainsi l importance de la spectroscopie Raman et la place réelle qu elle occupe comme technique de caractérisation. Ceci ouvre la voie à de nombreuses applications dans ce champ d études. / The investigations of the nonlinear (NL) effects that appear in ferroelectric crystals are becoming more and deeper. At the present time, the NL optical crystals are more and more used for the development of new coherent sources of visible radiations, frequency conversion, beside the detection and several signals and images transformations. A very representative crystal of this material class is lithium niobate, LiNbO3 (LN), that since its appearance never stop to surprise with revealing more and more its properties. In this work, we show how Raman microprobe can be used for the characterisation of the ferroelectric domain microstructures in periodically poled lithium niobate (PPLN). The Raman intensity of transverse and longitudinal modes of optical phonons was recorded across the stripe ferroelectric domains at the surface of a z-cut congruent PPLN sample. The change of integrated intensity was attributed to the influence of mechanical stresses and partially screened depolarization fields. So, we show the importance of Raman spectroscopy and the real place that it takes as a characterisation technique. This open the way for numerous applications in this field of studies.
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Organomagnesium Compounds in Benzene Solvent and Their Application in Synthesis of Organoberyllium CompoundsSelman, Charles M. 01 1900 (has links)
The work reported by D. Bryce-Smith and G. F. Cox, along with several recent publications describing experimental results designed to elucidate the long disputed question of the structure of the Grignard reagent in ether stimulated the work reported here, in an effort to obtain additional evidence of the structure of the organomagnesium complex in benzene solvent. Since the primary objective of this work was to prepare organoberyllium compounds using the organomagnesium complexes in hydrocarbon solvents, it seemed an insight into the structure of these complexes would be beneficial in this work. The techniques used and experimental evidence obtained from the structure elucidation of the ethereal Grignard reagent have been most helpful in organization of the methods used to study the structure of organomagnesium halide complexes in benzene solvent. It seemed that an insight into the structure of these organomagnesium halide complexes in hydrocarbon solvents would be beneficial in accomplishing the second objective of this work. This objective was to prepare organoberyllium compounds using the organomagnesium halide complexes prepared in hydrocarbon solvents.
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X-ray and neutron diffraction studies on the variation of the B conformation of deoxyribonucleic acid as a function of base sequenceLangan, Paul January 1990 (has links)
No description available.
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Preservation theorems for algebraic and relational models of logicMorton, Wilmari 30 July 2013 (has links)
A thesis submitted to the School of Computer Science,
Faculty of Science,
University of the Witwatersrand, Johannesburg
in fulfilment of the requirements for the degree of Doctor of Philosophy. Johannesburg, 15 May 2013 / In this thesis a number of different constructions on ordered algebraic structures
are studied. In particular, two types of constructions are considered: completions
and finite embeddability property constructions.
A main theme of this thesis is to determine, for each construction under
consideration, whether or not a class of ordered algebraic structures is closed
under the construction. Another main focus of this thesis is, for a particular
construction, to give a syntactical description of properties preserved by the
construction. A property is said to be preserved by a construction if, whenever
an ordered algebraic structure satisfies it, then the structure obtained through
the construction also satisfies the property.
The first four constructions investigated in this thesis are types of completions.
A completion of an ordered algebraic structure consists of a completely
lattice ordered algebraic structure and an embedding that embeds the former
into the latter. Firstly, different types of filters (dually, ideals) of partially ordered
sets are investigated. These are then used to form the filter (dually, ideal)
completions of partially ordered sets. The other completions of ordered algebraic
structures studied here include the MacNeille completion, the canonical
extension (also called the completion with respect to a polarization) and finally
a prime filter completion.
A class of algebras has the finite embeddability property if every finite partial
subalgebra of some algebra in the class can be embedded into some finite
algebra in the class. Firstly, two constructions that establish the finite embeddability
property for residuated ordered structures are investigated. Both of
these constructions are based on completion constructions: the first on the Mac-
Neille completion and the second on the canonical extension. Finally, algebraic
filtrations on modal algebras are considered and a duality between algebraic and
relational versions of filtrations is established.
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