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- Hol, Jeroen D., 1981-
(author)
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Sensor Fusion and Calibration of Inertial Sensors, Vision, Ultra-Wideband and GPS
- 2011
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Doctoral thesis (other academic/artistic)abstract
- The usage of inertial sensors has traditionally been confined primarily to the aviation and marine industry due to their associated cost and bulkiness. During the last decade, however, inertial sensors have undergone a rather dramatic reduction in both size and cost with the introduction of MEMS technology. As a result of this trend, inertial sensors have become commonplace for many applications and can even be found in many consumer products, for instance smart phones, cameras and game consoles. Due to the drift inherent in inertial technology, inertial sensors are typically used in combination with aiding sensors to stabilize andimprove the estimates. The need for aiding sensors becomes even more apparent due to the reduced accuracy of MEMS inertial sensors.This thesis discusses two problems related to using inertial sensors in combination with aiding sensors. The first is the problem of sensor fusion: how to combine the information obtained from the different sensors and obtain a good estimate of position and orientation. The second problem, a prerequisite for sensor fusion, is that of calibration: the sensors themselves have to be calibrated and provide measurement in known units. Furthermore, whenever multiple sensors are combined additional calibration issues arise, since the measurements are seldom acquired in the same physical location and expressed in a common coordinate frame. Sensor fusion and calibration are discussed for the combination of inertial sensors with cameras, UWB or GPS.Two setups for estimating position and orientation in real-time are presented in this thesis. The first uses inertial sensors in combination with a camera; the second combines inertial sensors with UWB. Tightly coupled sensor fusion algorithms and experiments with performance evaluation are provided. Furthermore, this thesis contains ideas on using an optimization based sensor fusion method for a multi-segment inertial tracking system used for human motion capture as well as a sensor fusion method for combining inertial sensors with a dual GPS receiver.The above sensor fusion applications give rise to a number of calibration problems. Novel and easy-to-use calibration algorithms have been developed and tested to determine the following parameters: the magnetic field distortion when an IMU containing magnetometers is mounted close to a ferro-magnetic object, the relative position and orientation of a rigidly connected camera and IMU, as well as the clock parameters and receiver positions of an indoor UWB positioning system.
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| 2. |
- Kaislahti Tillman, Päivi, 1958-
(author)
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Holocene climate and environmental change in high latitudes as recorded by stable isotopes in peat deposits
- 2012
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Doctoral thesis (other academic/artistic)abstract
- In this thesis, stable carbon and oxygen isotopes in α-cellulose isolated from Sphagnum fuscum moss remains were used as climate proxies. The main focus was to implement the methods in records from high latitude peatlands in the Northern Hemisphere (west-central Canada and north-eastern European Russia), reconstruct palaeoclimate of the studied regions during the Holocene, and evaluate the compatibility of results with other proxy records, especially tree-ring isotope time-series. The variation of stable carbon and oxygen isotope ratios (δ13C, δ18O) in different moss plant components was investigated and differences between untreated plants and α-cellulose extracts were evaluated. The impact of peat decay on the stable isotope proxies was studied by colorimetric and chemical (C/N) methods. Temperature reconstructions were developed based on the statistically significant relationship between δ13C and modern summer temperature records. Wet/dry periods were derived from a combination of δ18O records, macrofossil analysis, and a peat humification record in west-central Canada. A tentative reconstruction of snow depth in north-eastern European Russian tundra and northern taiga was based on δ18O records. The most promising result of the thesis is that stable carbon isotope variability in α-cellulose isolated from Sphagnum fuscum stems can be used to reconstruct and quantify palaeotemperatures several millennia back in time and to reveal both long-term and rapid climate shifts from peat archives.
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| 3. |
- Kurdve, Martin, 1971-
(author)
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Development of collaborative green lean production systems
- 2014
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Doctoral thesis (other academic/artistic)abstract
- This thesis deals with development of lean and green production systems from an action research point of view. The studies focus on Swedish-based automotive and vehicle industries and their aims to integrate sustainable thinking and environmental care into their operations management.Starting from operations management in manufacturing and corporate sustainable development, the research is built on how to integrate these two views into one production system. The systematic structure of a multiple-target improvement process with methodologies and tools designed to achieve the sustainability vision has been studied. Since lean as well as green production is based on the entire value chain, the research has gone beyond legal company limits and included the collaborative efforts between suppliers and customers in the value chain.The thesis includes six papers and describes approaches on how to implement integration, how to structure and integrate improvement management systems, how to set up an integrated monitoring and control system for the business and how to organise and redesign green lean tools and methodologies to support collaboration towards common targets.The results can be used for exploration and hypothesis formulation for further studies and development of integrated production systems and collaboration systems. The thesis helps answering how to integrate and implement company-specific green lean production systems.
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| 4. |
- Thomas, Laura D K
(author)
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Cadmium exposure and risk of kidney effects and bone fractures : population-based studies in England and Sweden
- 2013
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Doctoral thesis (other academic/artistic)abstract
- Cadmium (Cd) is a toxic metal with no beneficial biological function. The dissemination of cadmium to the surface environment, by industrial and agricultural practices, has led to increased human exposure. Food is the main source of exposure in the general non-smoking population however in areas close to industrial sources, contact with contaminated environmental media may also be important. Previous studies have shown toxic effects of cadmium on the kidneys and bone, however, considerable uncertainty remains over the exposure levels at which these toxic effects may start to occur and the clinical relevance of the early effects observed following long-term, low-level cadmium exposure. The aims of this thesis were: 1) To assess cadmium body burden and early signs of kidney dysfunction in a population exposed to industrial cadmium emissions and to develop and validate an air dispersion model of these emissions. 2) To identify urinary metabolites, associated with cadmium exposure, using metabolic profiling techniques. 3) To prospectively assess the association between validated estimates of dietary cadmium exposure and chronic kidney disease (CKD) incidence, kidney stone incidence, and fracture incidence, in two large population-based cohorts of men and women. In a population-based sample of 180 subjects, living close to a zinc smelter in Avonmouth, Southwest England, urinary cadmium concentrations (median = 0.22 nmol Cd/mmol creatinine) were in the same range as those where associations with kidney and/or bone effects have been observed previously. Three percent had concentrations above 1nmol Cd/mmol creatinine (~1μg/g) – the point of departure for tubular proteinuria set by the European Food Safety Authority in 2009. Modelled air cadmium concentrations from the smelter were strongly correlated with those from air monitoring sites (R2=0.84) and were a significant predictor of urinary cadmium (p=0.04). In a cross-sectional analysis, a significant dose-response relationship between urinary cadmium and one of the biomarkers of early tubular dysfunction (N- acetyl-β-d-glucosaminidase) was observed. Metabolic profiling identified six urinary metabolites, either related to mitochondrial metabolism or one carbon metabolism, associated with urinary cadmium. Two large population-based cohorts of men and women from Central Sweden were used to investigate the association between dietary cadmium exposure and incidence of CKD, kidney stones and fractures. Median dietary cadmium exposure levels in our study populations were 19μg/day in men and 13μg/day women. During an average of 12 years of follow-up, we ascertained 599 incident cases of CKD among men (481,591 person-years) and 253 among women (415,432 person-years). We did not observe an association between dietary Cd and rate of CKD in men, hazard ratio (HR) 0.97 (95% CI 0.77-1.21) or women HR 0.74 (95% CI 0.53-1.04), either before or after adjustment for potential confounders. During an average of 13 years of follow-up, we ascertained 707 incident cases of kidney stone among men (421,611 person-years) and 290 among women (403,575 person-years). Likewise, we did not observe an association between dietary Cd and rate of kidney stones in men HR 0.97 (95% CI 0.77-1.23) or women HR 0.99 (95%CI 0.89-1.43), either before or after adjustment for potential confounders. We ascertained 2,183 cases of any fracture and 374 cases of hip fracture, during a 10- year follow-up of 20,173 Swedish men. In the multivariable adjusted model, dietary cadmium was associated with a statistically significant 19% (HR: 1.19, 95%CI: 1.06- 1.34) higher rate of any fracture, comparing highest tertile with lowest. Hip fracture rates were also higher in the highest tertile of cadmium exposure but only statistically significant among never smokers, with a 70% (HR: 1.70, 95%CI: 1.04-2.77) higher rate. This study provides the first data on hip fracture rates in relation to cadmium exposure and is the first to report an excess risk of any fracture associated with long- term low-level cadmium exposure in men. The results of this thesis suggest that the adverse effects of cadmium exposure around the Avonmouth smelter may be detected in urinary biomarkers. In addition, the results of the prospective studies do not support a role of dietary cadmium exposure, at the level seen in the general population, in the development of CKD or kidney stones. However, the results do provide further evidence of increase fracture risk in relation to cadmium exposure. In conjunction with recent findings, the results of this thesis suggest that bone may be a more sensitive target of cadmium toxicity than the kidney, in terms of clinically relevant outcomes.
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