The fracture of brittle materials is of utmost importance for civil engineering and seismology applications. A different approach towards the aim of early identification of fracture and the prediction of failure before it occurs is attempted in this work. Laboratory experiments were conducted in a variety of rock and cement based material specimens of various shapes and sizes. The applied loading schemes were cyclic or increasing and the specimens were tested to compression and bending type loading of various levels. The techniques of Pressure Stimulated Current and Bending Stimulated Current were used for the detection of electric signal emissions during the various deformation stages of the specimens. The detected signals were analysed macroscopically and microscopically so as to find suitable criteria for fracture prediction and correlation between the electrical and mechanical parameters. The macroscopic proportionality of the mechanically stimulated electric signal and the strain was experimentally verified, the macroscopic trends of the PSC and BSC electric signals were modelled and the effects of material memory to the electric signals were examined. The current of a time-varying RLC electric circuit was tested against experimental data with satisfactory results and it was proposed as an electrical equivalent model. Wavelet based analysis of the signal revealed the correlation between the frequency components of the electric signal and the deformation stages of the material samples. Especially the increase of the high frequency component of the electric signal seems to be a good precursor of macrocracking initiation point. The additional electric stimulus of a dc voltage application seems to boost the frequency content of the signal and reveals better the stages of cracking process. The microscopic analysis method is scale-free and thus it can confront with the problems of size effects and material properties effects. The AC conductivity time series of fractured and pristine specimens were also analysed by means of wavelet transform and the spectral analysis was used to differentiate between the specimens. A non-destructive technique may be based on these results. Analysis has shown that the electric signal perturbation is an indicator of the forthcoming fracture, as well as of the fracture that has already occurred in specimens.

Woody plant expansion has been documented for decades in many different ecosystems, often due to anthropogenic disturbances to the environment and yielding vast changes in ecosystem functioning. While causes and consequences of woody expansion have been well documented, few studies have investigated functional traits of woody species that promote rapid expansion in range. My objective was to determine if hydraulic efficiency confers enhanced photosynthetic efficiency so that functional traits representing light and water use may be possible mechanisms facilitating woody encroachment into grasslands and forest understories. I quantified leaf-level light environment, photosynthetic activity, and hydraulic characteristics of three sympatric broadleaf evergreens of varying leaf life span (Ilex opaca, Kalmia latifolia, and Myrica cerifera) in a deciduous forest understory to understand seasonal intra- and interspecific ranges of broadleaf evergreen physiology. Additionally, I investigated the effects of age on physiological efficiency of M. cerifera across a chronosequence (i.e., space for time substitution) of shrub thicket development in order to understand possible age-related physiological mechanisms facilitating shrub expansion. Lastly, I determined functional traits and resulting physiology that contribute to rapid expansion and thicket formation of an invasive, deciduous, N-fixing shrub, Elaeagnus umbellata, and a native, evergreen, N-fixing shrub M. cerifera. When compared to co-occurring evergreen species, electron transport rate (ETR) of M. cerifera was nearly double that of I. opaca or K. latifolia in summer. Photosynthetic capacity was positively related to hydraulic capacity among understory evergreens. Furthermore, photosynthetic and hydraulic efficiency of M. cerifera remained consistent despite considerable differences in thicket age and development. Both similar and contrasting functional traits of E. umbellata and M. cerifera allowed for enhanced light capture and water movement, and reductions in subcanopy light penetration. Enhanced hydraulic and photosynthetic efficiency relative to co-occurring species contributes to rapid range expansion and thicket formation by promoting enhanced productivity and limiting successful colonization of other species. My results indicate that there may be suites of functional traits linked to expansive success and thicket-formation, yet differences in functional traits between native and invasive species represent alternative strategies leading to rapid growth and thicketization.

The main objective of this thesis is to efficiently disperse and align SWNTs in two different polymer matrices to obtain an orthotropic composite whose strength, stiffness and electrical properties depend on the orientation of the SWNTs. The SWNTs are successfully dispersed and aligned in a polyimide matrix and a polymer blend of UDMA/HDDMA. In-situ polymerization under sonication is used to disperse the SWNTs in polyimide matrix and sonication is used to disperse SWNTs in the UDMA/HDDMA matrix. In both cases, an electric field is used to align the SWNTs in the polymer matrices. In the polyimide, the SWNTs are aligned by electrospinning technique, and in (UDMA/HDDMA) the SWNTs are aligned by applying an AC electric field, while the composite is cured.The electrical and mechanical properties of randomly dispersed SWNT polyimide composites and SWNT/UDMA/HDDMA composite are measured. The dielectric constant and storage modulus of SWNT polyimide composite increased with SWNT concentration. Low percolation (0.06 wt%) and an increase of 113% in storage modulus with 0.2 wt% SWNTs, both indicate good dispersion of SWNTs in the polyimide matrix. The dielectric constants, conductivity for the unaligned SWNT/UDMA/HDDMA composite are isotropic. The electrical and mechanical properties of the randomly dispersed SWNT polyimide composite and SWNT/UDMA/HDDMA composite are used as references when analyzing the aligned counter parts. Different characterization methods are used to assess the alignment of the SWNTs in the polyimide and (UDMA/HDDMA) matrices. A variety of characterization techniques, i.e. microscopy, Raman spectroscopy, electrical conductivity, dynamic dielectric spectroscopy and dynamic mechanical analysis, indicate preferential alignment of SWNTs in two types of polymers: Polyimide and (UDMA/HDDMA). Optical microscope images showed alignment of the SWNTs in the UDMA/HDDMA composite. Inspection of the Raman spectra on aligned SWNT polyimide composite fibers and aligned SWNT/UDMA/HDDMA composite indicates a decrease in the intensity of the tangential peak of the SWNT with increase in the polarizer angle. The difference in the perpendicular and parallel Raman peaks indicate preferential alignment of SWNTs in both the polymer matrices. In the aligned polyimide composite, percolation transition is at 0.2 wt% SWNT concentrations when dielectric constant is measured parallel to the aligned SWNTs. But percolation transition is at 0.65 wt% SWNT concentrations when dielectric constant is measured perpendicular to the aligned SWNTs. Electrical measurements on aligned SWNT polyimide and UDMA/HDDMA composite are highly anisotropic. In both cases, the dielectric constant values parallel to the direction of SWNT alignment are higher than the values perpendicular to the direction of SWNT alignment. To analyze the resulting anisotropy in the dielectric constant, Bruggeman's effective medium approach is used. The effective medium theory predicts the effective dielectric constant of a composite with aligned anisotropic inclusions. The effective dielectric constant, perpendicular to the aligned inclusions and parallel to the aligned inclusions is estimated. The dielectric constant values of aligned SWNT polyimide and aligned SWNT/UDMA/HDDMA composites are compared to the experimental results. Both the values from the theory and experiment show anisotropy in dielectric constant. The theory indicated that the dielectric constant parallel to the aligned inclusions is highly influenced by the dielectric constant of the inclusion and the dielectric constant perpendicular to the aligned inclusions is highly influenced by the dielectric constant of the polymer matrix. Results from the different characterizing techniques indicate that SWNTs are successfully aligned in the polyimide matrix and (UDMA/HDDMA) matrix by electrospinning technique and by an AC electric field respectively.

This thesis deals with optimization of capillary electrophoresis conditions for the separation of unreacted substrate and products (cellobiose, glucose) generated by the enzymatic cleavage of cellotriose with enzyme cellobiase. The optimal separation electrolyte was shown to be a solution containing 30 mmol·dm-3 sodium hydroxide with addition of 1.0 mmol·dm-3 sodium phosphate and 1.0 mmol·dm-3 sodium phosphate dibasic (pH = 12.38). With this separation electrolyte calibration curves and repeatability were measured and the limits of detection and quantification were determined. The relative standard deviations of peak areas ranged up to 6.1 % and they did not exceed 0.2 % for the migration time. Limits of detection were determined in the range from 0.020 to 0.026 mmol·dm-3 and limits of quantification from 0.066 mmol·dm-3 to 0.085 mmol·dm-3 . Subsequently the enzyme reaction was monitored in offline setup. Furthermore, the offline procedure was automated and the relative standard deviation of cellodextrines after 30 minutes of hydrolysis was ranging up to 13.0 % of glucose and cellotriose and 3.0 % cellobiose using this automated method, which makes it suitable for semiquantitative and comparative measurements. The last part of the experiment was to carry out enzymatic reaction in online setup....

Le but de la thèse est de comprendre les mécanismes de localisation de particules (on parle de charges) dans des mélanges de polymères immiscibles. Ces travaux montrent que la localisation des charges de noir de carbone dans un mélange polypropylène (PP)/ poly-ε-caprolactone (PCL) est dominée par le rapport de viscosités et non par des paramètres thermodynamiques (liés au mouillage de la particule). La localisation des charges est expliquée par la compétition des forces de drainage visqueux s’exerçant sur les particules à l’interface. Le mécanisme de transfert des charges est mis en évidence par observation de la relaxation de gouttes de PCL chargées immergées dans une matrice PP. Le transfert se produit par un nouveau mécanisme, appelé « zip flow », qui consiste à l’érosion des gouttes au niveau des pointes. La maîtrise des différents paramètres étudiés permet de localiser les particules sélectivement à l’interface et d’obtenir des propriétés de conductivité à faible taux de charges. / The aim of this work is to understand mechanisms responsible for particles localisation in immiscible polymer blends. This study shows that carbon-black fillers localisation in polypropylene (PP)/ poly-ε-caprolactone (PCL) blends is strongly influenced by the viscosity ratio (rather than thermodynamic parameters through the wetting coefficient). The localisation of the fillers is explained by a competition of hydrodynamic forces applied on particles localised at the interface. The transfer of fillers is investigated at the droplet scale by observation of the relaxation of CB-filled PCL droplets suspended in PP matrix. CB particles are transferred from the PCL droplet to the PP matrix by a new mechanism, called “zip flow”, which involves the erosion of the droplet edges, leading to the extraction of particles localised there. The control of these parameters allows to localize fillers selectively at the interface and to reduce significantly the electrical percolation threshold.

A photovoltaic thermal solar collector (PVT) produces both heat and electricity from a single panel. PVT collectors produce more energy, for a given area, than conventional electricity and heat producing panels, which means they are a promising technology for applications with limited space, such as building integration. This work has been broken down into 3 subprojects focusing on the development of PVT technology. In the first subproject an experimental testing facility was constructed to characterise the performance of PVT collectors. The collectors under investigation were assembled by combining bespoke thermal absorbers and PV laminates. Of the two designs tested, the serpentine design had the highest combined efficiency of 61% with an 8% electrical fraction. The header riser design had a combined efficiency of 59% with an electrical fraction of 8%. This was in agreement with other results published in literature and highlights the potential for manufacturers of bespoke thermal absorbers and PV devices to combine their products into a single PVT device that could achieve improved efficiency over a given roof area. In the second project a numerical approach using computational fluid dynamics was developed to simulate the performance of a solar thermal collector. Thermal efficiency curves were simulated and the heat removal factor and heat loss coefficient differed from the experimental measurements by a maximum of 12.1% and 2.9% respectively. The discrepancies in the findings is attributed to uncertainty in the degree of thermal contact between the absorber and the piping. Despite not perfectly matching the experimental results, the CFD approach also served as a useful tool to carry out performance comparisons of different collector designs and flow conditions. The effect of 5 different flow configurations for a header collector was investigated. It was found that the most efficient design had uniform flow through the pipe work which was in agreement with other studies. The temperature induced voltage mismatch, that occurs in the PV cells of PVT collector was also investigated. It was concluded that the temperature variation was not limiting and the way in which PV cells are wired together on the surface of a PVT collector did not influence the combined electrical power output.

The objective of this study is to estimate 2-D spatial distribution of hydraulic conductivity (Ks) of Zhuoshui River alluvial fan, Taiwan, using groundwater level data from 88 wells and stream stage data from 4 gauging stations. In order to accomplish this analysis, wavelet analysis is first carried out to investigate the periodic cycles of groundwater level, precipitation, and stream stage. The results of the analysis show that variations of groundwater level and stream stage are highly correlated in terms of seasonal and annual periods. Subsequently, seasonal variations of groundwater level in response to stream stage variation are utilized to estimate the Ks spatial distribution by spatiotemporal cross correlation analysis, cokriging, and river stage tomography. Prior to applications of these methods to the alluvial fan, performances of each approach are evaluated and compared with reference field of a noise free synthetic experiment. It is found that all of the approaches could yield similar general spatial pattern of Ks. Nevertheless, river stage tomography seems to reveal a higher resolution of spatial Ks distribution. When the geologic zones are provided in river stage tomography analysis as prior information, the accuracy of estimated Ks values improves. Finally, results of the applications to data of the alluvial fan reveal that the apex and southeast of the alluvial fan are regions with relative high Ks and the Ks values gradually decrease toward the shoreline of the fan. These two areas are considered as the possible main recharge regions of the aquifer. It is also observed that Ks at northern alluvial fan is slightly larger than that at southern. These findings seem consistent with the geologic evolution of this alluvial fan.

This thesis concerns the formation, sintering and humidity dependent electrical behaviour of the spinel ceramic material nickel germanate, Ni(_2)Ge0(_4).Ni(_2)Ge0(_4) has been prepared via the solid state reaction between NiO and GeO(_2) over a range of temperatures, and characterised using a number of techniques. The sintering behaviour of pressed pellets of Ni(_2)Ge0(_4) has also been investigated, together with a characterisation of the microstructure of the sintered bodies. Substitutional doping of Ni(_2)GeO(_4) with Li as a replacement for Ni is found to promote a high degree of shrinkage in the sintering process, probably due to the formation of a liquid phase. XRD revealed that even when 10 % of the Ni atoms were replaced with Li, no change in the crystal structure could be detected. A C. impedance spectroscopy of Ni(_2)Ge0(_4) samples was used to investigate the humidity sensitivity of this material. Equivalent circuit analysis, based on a network of resistors and constant phase elements, shows that the humidity sensitivity is due to conduction in a surface layer of water, in agreement with the models currently popular in the Uterature. Measurement of the water adsorption isotherm of Ni(_2)Ge0(_4) in pellet form indicates that a single monolayer of water is formed at around 20 %R(_H), with an approximately linear increase in water layer thickness up to around 80 %R(_H), after which capillary condensation causes a large increase in the volume of adsorbed water. The information gained on the thickness of this layer of water has been correlated with the resistance of the layer measured by impedance spectroscopy, and subsequently used to provide evidence for a model of the humidity sensitive conduction. The conduction in the surface layer is thought to be due to dissociation of the water, where the amount of dissociation is exponentially dependent on the humidity.

This research validates electro-disinfection as a potential secondary ballast water treatment technology. Electricity applied to bacteria laden water produced bactericidal effects, reactive oxygen species and chlorine generation which annihilated bacteria. Evaluation of electro-disinfection experiments showed titanium electrodes had the maximum kill efficacy while disinfection with aluminum and stainless steel electrodes had lesser kill efficacy. A continuous flow electro-disinfection reactor was evaluated utilizing artificial brackish and fresh ballast water. Brackish water had a 100% bacteria kill efficiency utilizing titanium electrodes at a current density of 10 mA/cm2. Fresh water was augmented with the addition of salt to increase its electrical conductivity from 232 μS/cm to 873 μS/cm to ascertain 100% bacteria kill efficiency with titanium electrodes and a current density of 9.8 mA/cm2.

An experimental investigation of the electronic transport properties of bismuth telluride nanocomposite materials is presented. The primary transport measurements are electrical conductivity, Seebeck coefficient and Hall effect. An experimental apparatus for measuring Hall effect and electrical conductivity was designed, constructed and tested. Seebeck coefficient measurements were performed on a commercial instrument. The Hall effect and Seebeck coefficient measurements are two of the most important tools for characterizing thermoelectric materials and are widely used in the semiconductor industry for determining carrier types, carrier concentration and mobility. Further, these transport parameters are used to determine the thermal to electrical conversion efficiency of a thermoelectric material. The Boltzmann transport equation was used to analyze the Seebeck coefficient, carrier mobility and electrical conductivity as a function of carrier concentration for eleven samples. The relationship between the electronic transport and material/composite composition is discussed.