No description available.

No description available.

Acoustic emissions (AE) can provide information relating to the internal state of a deforming rock sample during laboratory testing and have been utilised to quantify damage progression for time-dependent failure modeling. However, the underlying physical mechanisms that produce AE in different materials and their evolution during the process of damage localisation are not fully understood, particularly in porous media. In order to investigate the sources of laboratory acoustic emissions, a moment tensor inversion was applied to data from triaxial compression experiments on Aue granite and Clashach sandstone. The moment tensor inversion was verified for granite, by comparison with results obtained using a more simplistic source analysis technique. In the non-porous Aue granite, AE sources exhibited a predominantly tensile behaviour in the early stages of AE activity. However, shear sources become dominant in the vicinity of the peak stress. In contrast, during deformation of the Clashach sandstone, which has a significant pre-existing porosity, AE sources are dominated by a collapse signature and generally involve a notable shear component. AE that have a predominantly shear mechanism are also a major contributor to the microscale deformation imaged by the technique, and dominate during shear localisation. A combination of correlation analysis and source analysis was used to elucidate the temporal and spatial evolution of the AE source mechanisms involved in the localisation process, as well as during a temporary hiatus in the progression to failure. The results support the concept that the cascade to failure requires the simultaneous involvement of a range of micromechanical behaviours to maintain the progression of localised damage, and eventual formation of a fault. Localisation of collapse mechanisms was not observed until the final approach to failure. Finally, AE sources produced during brittle deformation of the Clashach sandstone were characterised in detail and compared to microstructural observations representing the integrated effect of all times up to the end of the test, and including smaller structures that may have been formed insufficiently dynamically to produce AE. Equivalent focal mechanisms for these events are presented and the relative proportions of their volumetric and shear components considered. The results indicate that AE sources display a wide spectrum of micromechanical behaviour that is consistent with microstructural observations, indicating that AE mechanisms are representative of ongoing deformation processes within the sandstone. It is argued that moment tensor inversion of acoustic emissions is a powerful tool for elucidating the micromechanical evolution of damage, during the brittle deformation of rock.

Coal firing power stations represent the second largest source of global NOx emissions. The current practice of predicting likely exit NOx levels from multi-burner furnaces on the basis of single burner test rig data has been proven inadequate. Therefore, to further improve current NOx reduction technologies and assist in the assessment of NOx levels in new and retrofit plant cases, an improved understanding of the impact of burner interactions is required. The aim of this research is two-fold: firstly, to experimentally investigate isothermal flow interactions in multi-burner arrays for different swirl directions and burner pitches in order to gain a better understanding of burner interaction effects within multi-burner furnaces. Secondly, to carry out numerical modelling in order to determine turbulence models which give the best agreement to experimental data. Experimental investigations were carried out using flow visualisation for qualitative and 3D laser Doppler anemometry for quantitative measurements. Numerical modelling was performed using the computational fluid dynamics software, Fluent, to compare performance between k-ε, k- ω and RSM turbulence models. Experimental investigation showed that the recirculation zone of the chequerboard configuration is more sensitive to the change in pitch than that of the columnar configuration. Further, it was found that the smaller pitch is more sensitive to change in configuration than the wider pitch. The analysis of fluctuating components, u’, v’ and w’ showed that the burner flow is highly anisotropic at burner exit. Numerical investigation showed that the k-ω turbulence model consistently performed below the other two models. The statistical comparison between k-ε and RSM turbulence models revealed that, for prediction of the swirl velocity profiles, the RSM model overall performed better than the k-ε turbulence model. The visual and statistical analyses of turbulent kinetic energy profiles also showed that the RSM turbulence model provides a closer match to the experimental data than the k-ε turbulence model.

<p>Once thought to be predominantly the domain of cortex, multisensory integration has now been found at numerous sub-cortical locations in the auditory pathway. Prominent ascending and descending connection within the pathway suggest that the system may utilize non-auditory activity to help filter incoming sounds as they first enter the ear. Active mechanisms in the periphery, particularly the outer hair cells (OHCs) of the cochlea and middle ear muscles (MEMs), are capable of modulating the sensitivity of other peripheral mechanisms involved in the transduction of sound into the system. Through indirect mechanical coupling of the OHCs and MEMs to the eardrum, motion of these mechanisms can be recorded as acoustic signals in the ear canal. Here, we utilize this recording technique to describe three different experiments that demonstrate novel multisensory interactions occurring at the level of the eardrum. 1) In the first experiment, measurements in humans and monkeys performing a saccadic eye movement task to visual targets indicate that the eardrum oscillates in conjunction with eye movements. The amplitude and phase of the eardrum movement, which we dub the Oscillatory Saccadic Eardrum Associated Response or OSEAR, depended on the direction and horizontal amplitude of the saccade and occurred in the absence of any externally delivered sounds. 2) For the second experiment, we use an audiovisual cueing task to demonstrate a dynamic change to pressure levels in the ear when a sound is expected versus when one is not. Specifically, we observe a drop in frequency power and variability from 0.1 to 4kHz around the time when the sound is expected to occur in contract to a slight increase in power at both lower and higher frequencies. 3) For the third experiment, we show that seeing a speaker say a syllable that is incongruent with the accompanying audio can alter the response patterns of the auditory periphery, particularly during the most relevant moments in the speech stream. These visually influenced changes may contribute to the altered percept of the speech sound. Collectively, we presume that these findings represent the combined effect of OHCs and MEMs acting in tandem in response to various non-auditory signals in order to manipulate the receptive properties of the auditory system. These influences may have a profound, and previously unrecognized, impact on how the auditory system processes sounds from initial sensory transduction all the way to perception and behavior. Moreover, we demonstrate that the entire auditory system is, fundamentally, a multisensory system.</p> / Dissertation

Managing anthropogenic emissions in urban areas is a major challenge in sustainable environmental development for cities, and future changes and increasing urbanisation may increase this challenge. Systems perspectives have become increasingly important in helping urban managers understand how different changes may alter future emissions and whether current management strategies can efficiently manage these emissions. This thesis provides some systems perspectives that have been lacking in previous studies on modelling and managing future anthropogenic emissions in urban areas. The city of Stockholm, Sweden, was selected as the study site and studies about nitrogen, phosphorus and carbon were chosen, given world-wide urban eutrophication and global concerns about climate change. A substance flow analysis (SFA) structured model, comprising a source model coupled with a watershed model in an SFA structure, was developed to investigate future nutrient loading scenarios under various urban changes in small urban lake catchments. The results demonstrated that climate change potentially posed a greater threat to future nutrient loads to a selected lake catchment in Stockholm than the other scenarios examined. Another SFA-based study on future phosphorus flows through the city of Stockholm indicated that the best management option may depend on the perspective applied when comparing future scenarios of phosphorus flows and that both upstream and downstream measures need to be considered in managing urban phosphorus flows. An evaluation approach for examining current management plans and low-carbon city initiatives using the Driving forces-Pressure-States-Impact-Response (DPSIR) framework, was formulated. With such an evaluation approach, investigation of how well selected plans cover different aspects of the DPSIR framework and whether root causes and systematic measures are highlighted is possible. The results revealed that the current low-carbon city initiative in Stockholm falls within pressure-based, driver-orientated plans and that technical, institutional and cognitional measures are generally well covered. / <p>QC 20160510</p>

As the legislation on vehicle emissions is becoming more and more stringent, increasing attention has been paid to the fine particles emitted by diesel and gasoline vehicles. The high number emission of fine particles has been shown to have a large impact on the atmospheric environment and human health. Researchers have shown that gasoline engines, especially Gasoline Direct Injection (GDI) engines, tend to emit large amounts of small size particles compared to Port Fuel Injection (PFI) gasoline engines and diesel engines fitted with Diesel Particulate Filters (DPFs). As a result, the particle number emissions of GDI engines will be restricted by the EU6 legislation. The particulate emission level of GDI engines means that they would face some challenges in meeting the EU6 requirement. This thesis undertakes research in the following area. Firstly, the filtration efficiencies of glass fibre filters were quantified using a Cambustion Differential Mobility Spectrometer 500 (DMS500) to see if all of the particles from the sampled gas can be collected by the filters. Secondly, various valve timings and different injection modes such as double injection with a second injection after compression, single early injection and split early injection were implemented to measure the Particulate Matter (PM) emissions and combustion characteristics of a GDI engine under warm-up operating conditions. Thirdly, the techniques for removing volatile particles were investigated using a catalytic Volatile Particle Remover (VPR) and an Evaporation Tube (ET) with hot air dilution under various test conditions. The results show that for the glass fibre filters tested here, the transmission efficiencies of the particles are very low, indicating that PM sampling using fibre filters is an effective method of studying the particulate emissions from the engine. Particle number emissions using double injection with injection after compression were much higher than those with single injection during the intake stroke. Under 1200 rpm, 110 Nm cold engine operation, no reduction effect on PM emissions was shown by using split intake injection to further facilitate homogeneous mixture formation compared with single intake injection. Valve timings showed moderate effects on particulate emissions. Properly adjusted timing for exhaust valve closure led to reduced particulate emissions by a factor of about 2 and the combustion characteristics were not adversely affected much. The VPR temperature and exhaust residence time did not show much effect on the catalytic VPR performance once the mass flow rate of exhaust was above 0.09 g/s. Generally, the transmission efficiencies of the VPR follow the trends of the scaled PMP counting efficiency specification. Hot air dilution is effective in reducing the small size particles. At 23 nm, the transmission efficiencies are within the error range of the PMP specification. The catalytic VPR and the Evaporation Tube were all found to be effective in reducing the particle number of small size (nucleation mode) particles. Both systems have some particle loss mainly due to the physical effects of diffusion and thermophoresis. Until now, GDI engines have not been optimised for reducing particulate emissions as the focus has been on gaseous emissions and fuel economy. With careful re-optimisation of the catalyst light-off and engine calibration (especially for transients) then there is scope for GDI engines to meet forthcoming emissions legislation.

No description available.

Commercial aviation is a vital part of the United States economy. It generates over $1 trillion annually, which is more than 5% of the U.S. GDP, and produces approximately 10 million jobs. Every year there is an increase in commercial air traffic. This is attributed to expanding trade between states and other countries, which requires larger amounts of cargo aircraft in operation, and also catering to the growing number of middle and upper class passengers who travel for business and pleasure purposes. A rise in commercial aviation leads to the use of more aviation fuel on a monthly and annual basis. This in turn leads to escalated levels of combustion by-products from jet and turbofan engines into the atmosphere. The negative effects of these by-products range from producing poor air quality and consequent health hazards to contributing to global warming. This study is aimed at assessing the impacts of aircraft emissions on the local air quality in Corpus Christi using the Emissions and Dispersion Modeling System. Flight data for the study was obtained from the Department of Transportation's Research and Innovative Technology Administration. Analyses of the emissions were compared on monthly, annual, engine type and airline provider bases. Climatic, economic and anthropogenic factors were identified in the analyses.

The continued global reliance on fossil fuels with impact on resource depletion, human health, atmospheric pollution and environmental degradation has necessitated a global drive to integrate renewable fuels such as biodiesels. Biodiesels are described as “fuels composed of fatty acid methyl or ethyl esters and obtained from vegetable oils or animal fats”. Their use in energy generation could diversify the world’s energy mix, reduce fossil fuel dependence, reduce emissions and energy cost to bring about other economic benefits, especially for developing economies and rural communities with lack of adequate access to modern energy. A techno-economic and environmental life cycle assessment is however required to ensure that these fuels are fit for use in engines and meet any regulatory standard and sustainability criteria. This thesis has evaluated the use of Jatropha- and microalgae-biodiesel for power generation in two industrial gas turbines with open and combined cycle configuration. This was achieved using a techno-economic and environmental life cycle impact assessment framework. Comparative fuel assessments have been carried out between biodiesels and fossil fuels. Furthermore, the concept of microbial fuel degradation was examined in gas turbines. The thesis have identified Jatropha biodiesel as a worthwhile substitute for conventional diesel fuel, because it has close performance and emission characteristics to conventional diesel fuel with added advantage of being renewable. The consequent displacement of conventional diesel fuel with Jatropha biodiesel has significant environmental benefits. For economic viability and sustainability of gas turbine operated power plants, energy producers require a minimum monetary amount to recover the added cost of operating 100% Jatropha biodiesel. Other integration mechanisms are also available for utilizing the fuel in engines without compromising on plant’s economic performance. In worst case scenarios, where there are no government incentives, local conditions such as high life cycle cost of electricity, open opportunities for distributed and independent power generation from renewable fuels like Jatropha-biodiesel. Furthermore, this thesis has identified salient energy conversion processes that occur in gas turbine fuels, especially with biodiesels and developed a bio-mathematical model, Bio-fAEG to simulate these processes in gas turbines. This platform is a first step in quantifiable assessment and could enable a better understanding of microbial initiated processes.