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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.
1

Application of Gaussian Moment Closure Methods to Three-Dimensional Micro-Scale Flows

Lam, Christopher 25 August 2011 (has links)
A parallel, block-based, three-dimensional, hexahedral finite-volume scheme with adaptive mesh refinement has been developed for the solution of the 10-moment Gaussian closure for the modelling of fully three-dimensional micro-scale, non-equilibrium flows. The Gaussian closure has been shown to be a more effective tool for modelling rarefied flows lying within the transition regime than the Navier-Stokes equations, which encounter mathematical difficulties approaching free-molecular flows, and is computationally less expensive than particle-based methods for flows approaching the continuum limit. The hyperbolic nature of the moment equations is computationally attractive and the generalized transport equations can be solved in an accurate and efficient manner using Godunov-type finite-volume schemes as considered here. Details are given of the Gaussian closure, along with extensions for diatomic gases and slip-flow boundaries. Numerical results for several canonical flows demonstrate the potential of these moment closures and the parallel solution scheme for accurately predicting fully three-dimensional non-equilibrium flow behaviour.
2

Application of Gaussian Moment Closure Methods to Three-Dimensional Micro-Scale Flows

Lam, Christopher 25 August 2011 (has links)
A parallel, block-based, three-dimensional, hexahedral finite-volume scheme with adaptive mesh refinement has been developed for the solution of the 10-moment Gaussian closure for the modelling of fully three-dimensional micro-scale, non-equilibrium flows. The Gaussian closure has been shown to be a more effective tool for modelling rarefied flows lying within the transition regime than the Navier-Stokes equations, which encounter mathematical difficulties approaching free-molecular flows, and is computationally less expensive than particle-based methods for flows approaching the continuum limit. The hyperbolic nature of the moment equations is computationally attractive and the generalized transport equations can be solved in an accurate and efficient manner using Godunov-type finite-volume schemes as considered here. Details are given of the Gaussian closure, along with extensions for diatomic gases and slip-flow boundaries. Numerical results for several canonical flows demonstrate the potential of these moment closures and the parallel solution scheme for accurately predicting fully three-dimensional non-equilibrium flow behaviour.
3

Application of a ratiometric laser induced fluorescence (LIF) thermometry for micro-scale temperature measurement for natural convection flows

Lee, Heon Ju 15 November 2004 (has links)
A ratiometric laser induced fluorescence (LIF) thermometry applied to micro-scale temperature measurement for natural convection flows. To eliminate incident light non-uniformity and imperfection of recording device, two fluorescence dyes are used: one is temperature sensitive fluorescence dye (Rhodamine B) and another is relatively temperature insensitive fluorescence dye (Rhodamine 110). Accurate and elaborate calibration for intensity ratio verses temperature obtained using an isothermal cuvette, which was controlled by two thermo-bathes. 488nm Ar-ion laser used for incident light and two filter sets used for separating each fluorescence emission. Thermally stratified filed of 10mm channel with micro-scale resolution measured within 1.3?C uncertainty of liner prediction with 23?m x 23?m spatial resolution. Natural convection flows at 10mm channel also observed. The several difficulties for applying to heated evaporating meniscus were identified and a few resolutions were suggested.
4

Micro-scale study of multi-component ionic transport in concrete

Feng, Ganlin January 2018 (has links)
Corrosion of reinforcing steel in concrete due to chloride ingress is one of the main causes of the deterioration of reinforced concrete structures, particularly in marine environments. It is therefore important to develop a reliable prediction model of chloride ingress into concrete, which can be used to predict the chloride concentration profiles accurately to help to assess the service life for reinforced concrete structures. Cementitious materials are porous media with a highly complex and active chemical composition. Ionic transport in cementitious materials is a complicated process involving mechanisms such as diffusion, migration, ionic binding, adsorption and electrochemical interactions taking place in the pore solution of the materials. The process is dependent on not only the microstructural properties of the materials such as porosity, pore size distribution and connectivity but also the electrochemical properties of the pore solution including ionic adsorption and ion-ion interactions. This thesis presents a numerical study on the multi-component ionic transport in concrete with the main focus on the microscopic scale. This study first investigated the impact of the Electric Double Layer (EDL) on the ionic transport in cement-based materials. The EDL is a well-known phenomenon found in porous materials, which caused by the surface charges at the interface between solid surfaces and pore solutions. The numerical investigation is performed by solving the multi-component ionic transport model with considering the surface charges for a cement paste subjected to an externally applied electric field. The surface charge in the present model is taken into account by modifying the Nernst-Planck equation in which the electrostatic potential is dependent not only on the externally applied electric field but also on the dissimilar diffusivity of different ionic species including the surface charges. Some important features about the impact of surface charge on the concentration distribution, migration speed and flux of individual ionic species are discussed. Then a new one-dimensional numerical model for the multi-component ionic transport in concrete to simulate the rapid chloride migration test is proposed. Advantages and disadvantages of the traditional methods used to determine the local electrostatic potential, i.e. electro-neutrality condition and Poisson’s equation, are illustrated. Based on the discussion a new electro-neutrality condition is presented, which can avoid the numerical difficulties caused by the Poisson’s equation, and remain the non-linearity of the electric field distribution. This model with the new electro-neutrality condition is employed to simulate the RCM test to prove its applicability. The new model is promising in solving the multi-component ionic transport problems especially in microscopic scale. Lastly, a one-dimensional numerical investigation on the chloride ingress in a surface-treated mortar with considering the penetration of sealer induced porosity gradient was performed. The numerical model was carefully treated to apply governing equations of ionic transport to this situation of two pore structures, with every parameter clearly defined on the microscopic scale.
5

Climatic influences on the grapevine: a study of viticulture in the Waipara basin

Sluys, Shona Lee January 2006 (has links)
Climate is one of the most important factors influencing where wine grapes can be grown and the quality of wine produced from those grapes. A plants habitat has a profound influence on its growth and development. The surrounding climatic conditions at both the macro- and meso-scales influence the plant-climate miro-scale interactions. The main study site is the McKenzie Vineyard that is owned by Torlesse Wines. The climatic conditions of the surrounding Waipara region was also studied using climate data from the following vineyards; Canterbury House, River Terrace and Waipara West. The overall aim of this research is to improve understanding of the influence of the climatic environment on grapevine development at the meso- to micro-scale. The main findings of the research were firstly, that the most important climatic factor influencing grapevine development and growth is temperature and secondly that there is variability in the temperature across the Waipara Basin. Future research should be conducted for the entire growth season to gain a better understanding of how temperature influences the development of grapevine over the growing season as a whole.
6

Development and application of a rapid micro-scale method of lignin content determination in Arabidopsis thaliana accessions

Chang, Xue Feng 05 1900 (has links)
Lignin is a major chemical component of plants and the second most abundant natural polymer after cellulose. The concerns and interests of agriculture and industry have stimulated the study of genes governing lignin content in plants in an effort to adapt plants to human purposes. Arabidopsis thaliana provides a convenient model for the study of the genes governing lignin content because of its short growth cycle, small plant size, and small completely sequenced genome. In order to identify the genes controlling lignin content in Arabidopsis accessions using Quantitative Trait Locus (QTL) analysis, a rapid micro-scale method of lignin determination is required. The acetyl bromide method has been modified to enable the rapid micro-scale determination of lignin content in Arabidopsis. Modifications included the use of a micro-ball mill, adoption of a modified rapid method of extraction, use of an ice-bath to stabilize solutions and reduction in solution volumes. The modified method was shown to be accurate and precise with values in agreement with those determined by the conventional method. The extinction coefficient for Arabidopsis lignin, dissolved using acetyl bromide, was determined to be 23.35 g-iLcm-1. This value is independent of the Arabidopsis accession, environmental growth conditions and is insensitive to syringyl/guaiacyl ratio. The modified acetyl bromide method was shown to be well correlated with the 72% sulfuric acid method once the latter had been corrected for protein contamination and acid-soluble lignin content (R² = 0.988, P < 0.0001). As determined by the newly developed acetyl bromide method and confirmed by the sulfuric acid method, lignin content in Arabidopsis was found to be a divergent property. Lignin content in Arabidopsis was found to be weekly correlated with growth rate among Arabidopsis accessions (R² = 0.48, P = 0.011). Lignin content was also found to be correlated with plant height among Arabidopsis accessions (R² = 0.491, P < 0.0001).
7

Development of an Efficient Quasi-3D Microfluidic Flow Model and Fabrication and Characterization of an All-PDMS Opto-Microfluidic Flow Cytometer

Islam, Md Zahurul Unknown Date
No description available.
8

Development and application of a rapid micro-scale method of lignin content determination in Arabidopsis thaliana accessions

Chang, Xue Feng 05 1900 (has links)
Lignin is a major chemical component of plants and the second most abundant natural polymer after cellulose. The concerns and interests of agriculture and industry have stimulated the study of genes governing lignin content in plants in an effort to adapt plants to human purposes. Arabidopsis thaliana provides a convenient model for the study of the genes governing lignin content because of its short growth cycle, small plant size, and small completely sequenced genome. In order to identify the genes controlling lignin content in Arabidopsis accessions using Quantitative Trait Locus (QTL) analysis, a rapid micro-scale method of lignin determination is required. The acetyl bromide method has been modified to enable the rapid micro-scale determination of lignin content in Arabidopsis. Modifications included the use of a micro-ball mill, adoption of a modified rapid method of extraction, use of an ice-bath to stabilize solutions and reduction in solution volumes. The modified method was shown to be accurate and precise with values in agreement with those determined by the conventional method. The extinction coefficient for Arabidopsis lignin, dissolved using acetyl bromide, was determined to be 23.35 g-iLcm-1. This value is independent of the Arabidopsis accession, environmental growth conditions and is insensitive to syringyl/guaiacyl ratio. The modified acetyl bromide method was shown to be well correlated with the 72% sulfuric acid method once the latter had been corrected for protein contamination and acid-soluble lignin content (R² = 0.988, P < 0.0001). As determined by the newly developed acetyl bromide method and confirmed by the sulfuric acid method, lignin content in Arabidopsis was found to be a divergent property. Lignin content in Arabidopsis was found to be weekly correlated with growth rate among Arabidopsis accessions (R² = 0.48, P = 0.011). Lignin content was also found to be correlated with plant height among Arabidopsis accessions (R² = 0.491, P < 0.0001).
9

Climatic influences on the grapevine: a study of viticulture in the Waipara basin

Sluys, Shona Lee January 2006 (has links)
Climate is one of the most important factors influencing where wine grapes can be grown and the quality of wine produced from those grapes. A plants habitat has a profound influence on its growth and development. The surrounding climatic conditions at both the macro- and meso-scales influence the plant-climate miro-scale interactions. The main study site is the McKenzie Vineyard that is owned by Torlesse Wines. The climatic conditions of the surrounding Waipara region was also studied using climate data from the following vineyards; Canterbury House, River Terrace and Waipara West. The overall aim of this research is to improve understanding of the influence of the climatic environment on grapevine development at the meso- to micro-scale. The main findings of the research were firstly, that the most important climatic factor influencing grapevine development and growth is temperature and secondly that there is variability in the temperature across the Waipara Basin. Future research should be conducted for the entire growth season to gain a better understanding of how temperature influences the development of grapevine over the growing season as a whole.
10

Development and application of a rapid micro-scale method of lignin content determination in Arabidopsis thaliana accessions

Chang, Xue Feng 05 1900 (has links)
Lignin is a major chemical component of plants and the second most abundant natural polymer after cellulose. The concerns and interests of agriculture and industry have stimulated the study of genes governing lignin content in plants in an effort to adapt plants to human purposes. Arabidopsis thaliana provides a convenient model for the study of the genes governing lignin content because of its short growth cycle, small plant size, and small completely sequenced genome. In order to identify the genes controlling lignin content in Arabidopsis accessions using Quantitative Trait Locus (QTL) analysis, a rapid micro-scale method of lignin determination is required. The acetyl bromide method has been modified to enable the rapid micro-scale determination of lignin content in Arabidopsis. Modifications included the use of a micro-ball mill, adoption of a modified rapid method of extraction, use of an ice-bath to stabilize solutions and reduction in solution volumes. The modified method was shown to be accurate and precise with values in agreement with those determined by the conventional method. The extinction coefficient for Arabidopsis lignin, dissolved using acetyl bromide, was determined to be 23.35 g-iLcm-1. This value is independent of the Arabidopsis accession, environmental growth conditions and is insensitive to syringyl/guaiacyl ratio. The modified acetyl bromide method was shown to be well correlated with the 72% sulfuric acid method once the latter had been corrected for protein contamination and acid-soluble lignin content (R² = 0.988, P < 0.0001). As determined by the newly developed acetyl bromide method and confirmed by the sulfuric acid method, lignin content in Arabidopsis was found to be a divergent property. Lignin content in Arabidopsis was found to be weekly correlated with growth rate among Arabidopsis accessions (R² = 0.48, P = 0.011). Lignin content was also found to be correlated with plant height among Arabidopsis accessions (R² = 0.491, P < 0.0001). / Forestry, Faculty of / Graduate

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