Thesis (Ph.D.)--Victoria University of Wellington, 2007. / "Version 1.1, 16 August 2007 (including corrections)" Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

Thesis (Ph.D.)--York University, 2005. Graduate Programme in Earth and Space Science. / Typescript. Includes bibliographical references (leaves 260-268). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pNR11542

The condensation of simple aliphatic and aromatic aldehydes and of ketones with cyclic and acyclic glucose derivatives has been considerably investigated and, thus, isopropylidene, ethylidene, benzal and many similar and related compounds are well known: for example, benzaldehyde condenses readily with methyl glucoside and this typical reaction may be illustrated by the equation which is formulated on the following page. It is, therefore, a continuation of this work to attempt to effect similar condensations employing, as the carbonyl component, open-chain sugar derivatives which possess a free aldehydic group and to determine whether such ‘glucosydlidene' compounds are available.

Conselho Nacional de Desenvolvimento Cientifico e Tecnológico / Fundação Carlos Chagas Filho de Amparo a Pesquisa do Estado do Rio de Janeiro / Nesta tese abordaremos os processos de fotoassociação em condensação de Bose- Einstein. Estes podem ser resumidos da seguinte forma: um condensado formados por átomos, inicialmente no estado fundamental, é iluminado com laseres de freqüência adequada, de tal modo que os átomos se combinem em moléculas. Tudo isto sem que o condensado deixe de existir por conta de instabilidades envolvidas neste processo. O que acabamos de descrever tem um equivalente na ótica quântica: a geração de segundo harmônico, cujas equações são semelhantes as do condensado. A natureza mais complexa das interações entre átomos, bem como a consideração de graus de liberdade internos, inclui efeitos potencialmente mais interessante que os encontrados com a luz. A quantidade de fenômenos que pode ser abordada é muito grande. As ressonâncias de Feshbach, por exemplo, são capazes de alterar a natureza da interação interatômica. Também podemos ter dois átomos fermiônicos formando uma molécula bosónica. Há efeitos de interferência entre dois condensados e estudos teóricos concernentes a fase relativa entre eles. Também é importante citarmos os estudo sobre vórtices e momento angular, enfim, há todo um zoológico de idéias a serem propostas teoricamente ou experimentalmente. Assim como em 1911 repentinamente surgiram novas áreas de estudo devido a descoberta da supercondutividade, aqui ocorre algo semelhante, uma fronteira da física foi aberta e devemos explora-la até que novos limites sejam alcançados.

L'aviation civile a connu une forte croissance et occupe actuellement une place importante dans l'économie mondiale. L’intensification du trafic aérien s’accompagne d’une augmentation importante des émissions de gaz à effet de serre et d’aérosols dans la haute troposphère, ceux-ci contribuent au réchauffement climatique. Les particules de suie rejetées dans la haute troposphère peuvent agir comme noyaux de condensation et induire la formation de gouttelettes d'eau ou de particules de glace qui constituent les traînées de condensation (contrails). Celle-ci, peuvent persister et évoluer en formant des nuages artificiels, sous forme de cirrus induit. Ce travail vise à acquérir une meilleure connaissance du rôle des particules de suie dans le processus de formation des contrails. Pour mieux comprendre ce phénomène, nous avons déterminé la fraction activée et la sursaturation critique des suies avec un dispositif expérimental permettant de prélever les suies dans une flamme de laboratoire. Nous avons dans un premier temps déterminé les propriétés hygroscopiques des suies fraîches. Nous avons également évalué l’impact de la composition chimique du carburant (kérosène et diesel), la maturité et la taille des suies sur les propriétés hygroscopiques. Nous nous sommes ensuite intéressés à l’impact de différents vieillissements atmosphériques sur les propriétés hygroscopiques des suies kérosène. Enfin, nous avons estimé le paramètre d’hygroscopicité κ des suies fraîches (kérosène et diesel) et celui des suies ayant subi un vieillissement atmosphérique. / Civil aviation has traditionally experienced faster growth than most other industries, and currently is a leading part of the global transport economy. In parallel to the civil aviation growth, larger and larger amount of greenhouse gases and aerosol particles are emitted in the high troposphere. Especially, aerosol emissions can trigger the formation of condensation trails (contrails) that may persist and eventually evolve in cirrus-like artificial clouds. Soot particles released on the high troposphere may act as precursors for the water droplets or ice particles of which contrails are formed, ultimately initiating the formation of clouds in conditions where they would not otherwise persist. In this work we aim to gain better insights on the role of soot in the contrail formation process. To better understand this phenomenon, we determined the activated fraction and the critical supersaturation of soot sampled from laboratory flames. We evaluated the hygroscopic properties of fresh soot. We studied the influence of sampling method, particle size and maturity of soot. We were then interested in the impact of different atmospheric aging on the hygroscopic properties of kerosene soot. Finally, we determined the hygroscopicity parameter κ of fresh soot and aging soot (diesel and kerosene).

In this thesis a number of aspects on possible manipulation of Bose-Einstein condensate in trapped atomic gases is investigated. First, a model for atom optical experiments involving Bose condensates is proposed and numerical simulations are presented to illustrate its characteristics. We demonstrate ways of focusing and splitting the condensate by modifying experimentally adjustable parameters. We show that there are at least two ways of implementing atom optical elements: one may modulate the interatomic scattering length in space, or alternatively, use a sinusoidal, externally applied potential. The temporal evolution of quasiparticle excitations is studied via the Gross-Pitaevskii Equation. Nonlinear mode mixing of quasiparticles is introduced, and is observed using a quasiparticle projection method. This is used as a basis of time-dependent finite temperature simulations, which we argue to be valid under regimes of high occupation number. An illustration via a closely related evaporative cooling simulation is provided. A phenomenological damping formalism for superfluidity near the λ point is adopted to describe the damping of excitations in a Bose-Einstein condensate. An estimate for the damping parameter is found. The damping formalism as a numerical tool to calculate the ground eigenstate of the condensate is explored. A novel, experimentally realisable interferometry for Bose-Einstein condensates using near-field diffraction is proposed. The scheme is based on the phenomenon of intermode traces or quantum carpets; we demonstrate the structured spatio-temporal pattern for the dilute, atomic Bose-Einstein condensate. The pattern is found to change with temperature, which allows us to perform interferometric temperature measurements. Finally, an output coupler for Bose-Einstein Condensates based on stimulated Raman transition is investigated. The spectrum and coherence are calculated for an atomic beam slowly coupled out of a trap containing a partially condensed Bose gas at finite temperatures. A number conserving Hartree-Fock-Bogliubov formalism has been used to incorporate finite temperature effects. Various different processes are found to become dominant for a suitable choice of the coupling parameters.

Doctor of Philosophy / Department of Mechanical and Nuclear Engineering / Melanie M. Derby / Power plants are significant water users, accounting for 15% of water withdrawals worldwide. To reduce water usage, compact condensers are required to enable air-cooled condensers and reduce infrastructure costs. Steam flow condensation was studied in 0.952-mm and 1.82-mm hydraulic diameter mini-gaps in an open loop experimental apparatus. The apparatus was validated with single-phase flow. Flow condensation experiments were conducted for a wide range of steam mass fluxes (i.e., 35–100 kg/m²s) and qualities (i.e., 0.2–0.9) in hydrophilic copper and hydrophobic Teflon-coated channels. Water contact angles were 70° and 110° on copper and Teflon, respectively, and in general, filmwise condensation was the primary condensation mode in the hydrophilic channel and dropwise condensation was the primary mode observed in the hydrophobic channel. Pressure drops were reduced by 50–80% in the hydrophobic channels. Condensation heat transfer was enhanced by 200–350% in hydrophobic mini-gaps over hydrophilic mini-gap due to dropwise condensation. Droplet dynamics (e.g., nucleation, coalescence and departure) were quantified during dropwise condensation. A model was created which includes droplet adhesion and drag forces for droplet departure diameters which were then correlated to heat transfer coefficients. An overall mean absolute error of 9.6% was achieved without curve fitting. Noncondensable gases can reduce heat transfer in industrial systems, such as power plants due to the additional layer of thermal resistance from the gas. Condensing steam-nitrogen experiments were conducted for nitrogen mass fractions of 0–30%; the addition of nitrogen reduced heat transfer coefficients by up to 59% and 30% in hydrophilic and hydrophobic mini-gaps, respectively. It was found that during dropwise condensation, the noncondensable layer was perturbed by cyclical droplet motion, and therefore heat transfer coefficients were increased by 2–5 times compared with filmwise condensation of the same mass fraction of nitrogen.

D.Ing.

Though heating, insulation, wall claddings and cavity-wall construction are considered as measures for remediating moisture and condensation in buildings, ventilation of wall cavities has however become a mantra among architects and other building professionals. Holes of any size and shape are made and located on building facades based on the accepted wisdom that a little air movement will keep the wall cavities dry. Whilst ventilation has been found to be successful in the control of moisture and condensation in rooms and larger enclosures, there is however insufficient understanding of how it works in thin spaces with high aspect ratios, such as the wall cavities studied in this thesis.In order to put in place good control and management practices in the remediation of moisture and condensation in vertical wall cavities by natural ventilation, it is vital to understand the dynamics of airflow in these cavities. In this thesis therefore, different size and shape of slots were employed to numerically investigate the effects of size, spacing and number of the slots on the characteristics of the velocity fields (patterns of airflow and distributions of velocity) in different cavity models. The Reynolds-Averaged-Navier-Stokes (RANS) methodology was employed to simulate the cavity flows under different modelling conditions using FLUENT. The BS 5925 model, an empirical relation for predicting ventilation rates in rooms and other larger enclosures, was employed and modified to predict ventilation rates in these cavities. Experimentally, the mapping of the airstreams in these cavities was obtained under similar reference (inlet) wind speeds employed for the numerical investigations.The results of this study show that there exists a potential at higher wind speeds for natural ventilation in the remediation of moisture and condensation in the cavities of vertical walls. The steady state approach employed in the RANS-based computation of cavity flows in this thesis averages out the peak values of air velocities and therefore gives no information about regions of maxima or minima velocity values even at higher wind speeds. This makes the predicted air change rates insensitive to the inlet air velocities from the ventilation slots and therefore makes the results more applicable for long term control and management of moisture in these cavities. In order to therefore put in place short, medium and long term plans for remediation of moisture in these wall cavities, a time-dependent computation is required. This will also allow the efficiency of the cavity ventilation to be properly assessed. Using the modified BS 5925 model, reasonable predictions were obtained for the air change rates of the wall cavities with the different size of ventilation slots employed. Close agreements are also obtained at lower and higher wind speeds between the predicted ventilation rates from the modified BS 5925 model and the experimental results employed as benchmark for validating the results.