Chemical abundances as measured from stellar spectral lines are often subject to uncertainties due to lack of accurate data for inelastic collisions, which is needed for non-local thermodynamic equilibrium (non-LTE) modelling. For cool stars, understanding of collision processes with electrons and hydrogen atoms is required to achieve high precision measurements. In this thesis, I have investigated the role of these collisions on the non-LTE formation of Li and Mg spectral lines in late-type stars. In the case of Li, electron impact excitation processes were calculated using the R-matrix with pseudo states method and the results found to agree well with recent calculations using the convergent close-coupling technique. These modern data were employed in non-LTE calculations by updating an existing model atom, which already included modern data for hydrogen collision processes. Our results were compared with calculations using older semi-empirical approximation calculations and only small differences were found: about 0.01 dex (~ 2%) or less in the abundance corrections. We therefore conclude that the influence of uncertainties in the electron collision data on non-LTE calculations is negligible. Indeed, together with the collision data for the charge transfer process Li + H ↔ Li+ + H- now available, and barring the existence of an unknown important collisional process, the collisional data in general is not a source of significant uncertainty in non-LTE Li line formation calculations. In the case of Mg, electron impact excitation processes were again calculated with the Rmatrix with pseudo states method, and used together with recent hydrogen collision calculations to build and test a model atom, without free parameters, for non-LTE modelling. Both electron and hydrogen collision processes, including charge transfer and excitation, are found to be important thermalising agents in various cases. The modelled spectra agree well with observed spectra from benchmark stars in the optical and infrared. The modelling predicts non-LTE abundance corrections ∆A(Mg)NLTE–LTE in dwarfs, both solar metallicity and metal-poor, to be very small (of order 0.01 dex), even smaller than found in previous studies. In giants, corrections vary greatly between lines, but can be as large as 0.4 dex. Results of calculations in a large grid of 1D model atmospheres are presented, and the implications for studies of Mg discussed. The propagation of uncertainties in the inelastic collision data to those in stellar abundances is investigated, and found to lead to small uncertainties, once again typically less than 0.01 dex (2%), although for few stellar models in specific lines (e.g., metal-poor suns, in the 7691 Å line) uncertainties can be as large as 0.03 dex (7%).

Did you know that in 2008 the largest publicly listed companies in the world caused environmental damage for a total estimated cost of $2.15 trillion, accounting for 35% of total global environmental costs caused by human activity? Or did you know that three million people die every year because of outdoor pollution made by vehicles and factories? Most companies have some sort of environmental policy that aims to reduce waste and pollution, but there are few that aim to become a climate neutral business. Our study has the intention to find out why some companies are willing to do something extra for the environment by voluntary compensate for their emissions through carbon offsets. Previous research has shown that there is a lack of understanding regarding the motivations to reduce emissions and that there is a need for studies to find out motivations for why companies buy voluntary carbon offsets, which leads us to our problem definition: What motivates companies to buy voluntary emission offsets? We developed four sub-purposes that helped us in our journey towards an answer to our research question. These were: identify incentives for emission offsetting, important aspects when evaluating which projects to support, if and how companies are communicating their offsetting activities and whether the possibility of buying emission offsets reduce incentives for companies to decrease their own emissions. Our degree project is written on commission for Respect Climate, a sustainability consultancy that operates in the area of Scandinavia. They help their customers to reduce their emissions, make climate calculations and offset emissions. Our aim with our conclusions of our degree project is to help Respect Climate to market their services to potential customers. As our degree project focuses on underlying motivations behind their customers’ behavior, we have chosen to do a qualitative study. First we implemented two interviews with employees at Respect Climate, which acted as a foundation to our interviews with four of their business customers. Further, we chose to collect communication data from their customers’ annual reports and websites in order to get a third dimension to our study. Our conclusions have shown that the primary motivation for engaging in emission offsetting is doing something good for the environment, but other incentives within the social and economic aspects of the Triple Bottom Line are expressed as well.

This thesis presents a system to display Structural Health Monitoring (SHM) data interactively at multiple scales that range from milliseconds to years. Typically, visualizing large SHM datasets produce static plots that take significant time to render. Our system improves upon standard tools by providing an interactive interface and a speed-optimized binning algorithm. Using the interface, a user is able to view data collected from a bridge's sensors at multiple scales in a web browser. This allows a user to visually inspect the entire range of their data to see both short and long-term trends. To render the data, the system uses a binning algorithm to calculate a five-number summary of a range of data. Those bins are combined to generate increasingly high levels of bins, which are then rendered as a binned line chart. The chart is rendered using a standard web browser on both desktop and mobile devices.

In order to create a machining line layout that supports the principles of lean a systematic approach is needed to ensure that a wide range of factors are taken into consideration. Despite this, many companies today design new layouts mainly considering delivery times of machines and equipment, and available space in the factory. A combined literature and case study has aimed to identify the most important factors in a lean line layout and a supporting structure to apply these in the design or redesign of automated machining lines. Highly automated machining environments mainly distinguish themselves from the more thoroughly studied area of assembly line layouts in two ways. Primarily, automated machining lines separate the operator from the actual processing, making line balancing and productivity less dependent on the workstation design around the operator. Secondly, automated machining lines often involve a higher level of complexity, leading to a more comprehensive work load, requiring longer training times but also offering less repetitive assignments. Automation offers improved productivity, quality and ergonomics, but if the acquisition and allocation of automation is not substantiated by a well-developed strategy, automation risks contradicting lean principles by creating a more complex, rigid layout that places the machines in the center instead of the workers. Factors that are important in the design of the typically less automated assembly lines, such as minimizing the walking distance of the operator and rotating stations to provide meaningful work assignments, must in an automated machining environment give way to factors like visualization, material flow and maintenance. Visualizing a factory helps operators and managers learn and understand the factory better. Problems can be detected and corrected faster and disturbances in production can thus be reduced. A good material flow is straight with no intersecting flows, triggered by downstream demand and reduces unnecessary buffers and WIP that bind up capital and consume space. Finally, since the machines rather than the operators produce, a good maintenance is required to avoid unplanned stops. The value of teamwork and humans in production which are strongly advocated within lean remain important also in automated machining lines but acquires a new content compared to assembly lines. Teamwork in automated machining environments occur within a group of lines rather than in a single line and it is a major factor when it comes to competence development, production planning and worker satisfaction. While teamwork in assembly lines works to balance the production flow within the line, teamwork in automated machining lines has little or no effect on the line balancing. However, joint efforts in setups and in case of machine failures or worker absence help increasing productivity, and potentially smooth the production at the plant in its entirety. The empirical studies showed that there is no standardized way of working with machining line layout design and redesign, and factors considered were often coincidental and dependent on the functions and priorities of the participants at different layout meeting. To ensure that all factors are taken into consideration a supporting tool where the most important factors were divided into ten categories was developed. Layouts are evaluated and rated on one category at a time to support a systematic way of working. Ongoing discussions, adjustments and improvements to better comply with the factors are encouraged.

Bioprocesses carried out for the production of fuels and other value-added co-products require effective process control strategies. The objective of this research is to apply Titrimetric Off-Gas Analysis (TOGA) for the on-line estimation of fermentation end products using Clostridium thermocellum. The hydrogen ion production, gaseous H2 and CO2, soluble H2 and CO2, as well as ethanol in the liquid phase and vapour phase, were monitored. All parameters, except the dissolved gases, showed good correlation with concurrent off-line analysis. The resulting mass and electron balances were close to theoretical values, and not significantly different from those determined using off-line analysis. Liquid-to-gas mass transfer limitations caused supersaturation of H2(aq) for a wide-range of operating conditions, and on average, ranged between 8-14 times the expected value at thermodynamic equilibrium. The supersaturation of CO2(aq) was conditional, and could be alleviated by increased sparging at agitation such that no significant mass transfer limitation was present. Simultaneous data on ethanol, CO2, and H2 could be obtained with the MIMS probe placed adjacent to the liquid surface in the reactor headspace. From this data, a metabolic model was proposed for the on-line estimation of formate and acetate using a mass balance and an electron balance. The model estimated formate concentrations with reasonable accuracy. Acetate predictions agreed with the qualitative trends, but the concentrations were inaccurate in comparison with off-line analysis. It was demonstrated that the sensor could provide on-line information on all major end-products synthesized by C. thermocellum. In conclusion, TOGA is a valuable instrument for the on-line monitoring and study of fermentation processes for cellulosic biofuels production

No description available.

No description available.

Previous work on modal analysis of mooring lines has been performed from different theoretical formulations. Most studies have focused on mooring lines of a single homogeneous material, and the effect of added mass and damping produced by the water has not been examined deeply. The variational formulation approach, employed in this research to perform a modal analysis, has been useful to study the behavior of several realistic mooring lines. The cases presented are composed from segments of materials with different mechanical characteristics, more similar to those in current offshore projects. In the newly proposed formulation, damping produced by transverse motion of the mooring line through the surrounding water has been added to the modal analysis. The modal analysis formulation applied in this work has been verified with calculations from commercial software and the results are sufficiently accurate to understand the global behavior of the dynamics of mooring lines with the damping produced by the sea water. Inclusion of linearized drag damping in the modal analysis showed that the modal periods of the mooring systems studied depend on the amplitude of the transverse motion of the mooring line. When more amplitude in the motion is expected more damping is obtained. Two realistic designs of mooring lines were compared: one made up with a main insert of steel rope, called “Steel System”, and one composed by a main insert of polyester, named “Polyester System”. Comparing the natural periods of both systems, the Steel System appears to be safer because its fundamental natural period is more distant from the wave excitation periods produced by storms. The same happens considering the wave excitation periods produced by prevailing seas. In this case the natural periods of the Polyester System are nearer to the wave excitation periods causing fatigue loads. The transverse mode shapes for lateral motions of the mooring lines are observed to be continuous and smooth across material transitions, such as transitions between chain and wire rope and transitions between chain and polyester rope. This behavior is not always observed in the tangential mode shapes for the Polyester System where significant differences in dynamic tension seem to be present in the specific cases studied.

Thesis (PhD)--University of South Australia, 1996

Assembly Sequence Planning (ASP) is part of Assembly Planning. The assembly sequence is the most important part of an assembly plan. Assembly has an important share in both lead time and cost of a product. Therefore, its optimisation is necessary to ensure the competitivity of manufactured goods. The aim of this thesis is the optimisation of assembly sequences for mechanical products, for real/realistic problems and constraints. This thesis represents an integrated approach in assembly sequence planning and optimisation. It tackles real problems by building the generality in the models. The ASP problem is a large scale, highly constrained, combinatorial problem, with an extraordinarily diverse character. Assembly can address sequential or non-sequential, linear or non-linear, monotone or non-monotone, coherent or non-coherent assembly plans or any combination of those, involving rigid, elastic, non elastic, solid, liquid or gaseous components or subassemblies. To be applicable in practice and useful, an assembly sequence planning and optimisation algorithm has to be general enough to accommodate any type of assembly plan and component. For this reason, modelling becomes critically important. A model has been developed for the assembly process, to determine what the assembly process is in mathematical terms. A second model has been developed to model/represent assembly plans as chromosomes that encode any type and combination of assembly plans. Another model has been developed for modelling/representing products for assembly. This model constitutes the database containing all information necessary for generating feasible assembly sequences, for any type of component and subassembly. A framework has been developed for the definition of a fitness function to assess the quality of an assembly sequence and plan from optimisation criteria. Solving the ASP problem (prior to its optimisation), implies generating a sequence to assemble an n-part product given its description and a number of supplementary constraints. A guided search algorithm has been developed to solve the ASP problem. To optimise the ASP, Genetic Algorithms (GA) were used in this research. The GA has a classic structure and modified genetic operators: it only generates and manipulates legal and feasible chromosomes. An initial population of feasible chromosomes is generated through guided search. This population, then, undergoes transformations over a number of generations, through crossover and selection. The crossover, based on the guided search algorithm, is also designed to produce only legal chromosomes. The selection is a classical operation, through a weighed roulette algorithm. It operates on an extended population of parent and children chromosomes. The output of the GA is a population of chromosomes with a high fitness value, corresponding to optimal/near optimal assembly sequences, from which the best one is selected. A number of examples are used in each chapter to illustrate each significant aspect considered. A final example illustrates the application of the whole algorithm to produce optimised assembly sequences for an industrial-size product. / thesis (PhD)--University of South Australia, 2003.