A Non-recursive Solution Method for Fixed-interval Smoothing Problems Applied to Short-term Inertial Navigation

This study focuses on short-term inertial navigation performed within a fixed time interval; one which is already over before the gathered data is processed. This yields a fixed-interval smoothing problem. The time interval is assumed to be short in order to simplify the equations related to inertial navigation without causing excessive errors to the estimates of attitude, velocity, and position, these values being the solutions to the problem. The aim is to develop a new solution method for applications of inertial navigation, particularly in sports, where the objective is often to ensure that the hardware can be integrated with the relevant equipment. This obviously imposes serious constraints on the size and mass of the used navigation system. Therefore, this study focuses on the use of consumer-grade sensors, and new calibration methods are also presented to improve the performance of such sensors. The traditional approach to fixed-interval smoothing problems is based on the principle of combining two recursive filters, which are run forwards and backwards in time. This study, however, uses a non-recursive solution method. The advantages of this approach are best described with a single word: flexibility. Firstly, with this solution method there is no need to decide whether the fixed-interval smoothing problem is based on initial or boundary values, i.e. whether the ordinary differential equation describing the time evolution of the system is posed as an initial value problem or a boundary value problem. Secondly, it allows many forms of additional information to be used, which can be related to an arbitrary number of time instances. And thirdly, this solution method produces accurate results in the absence of any detailed knowledge of the involved errors. The proposed non-recursive solution method uses a specific combination of the constructed state and observation equations in order to find a solution to the problem. The problem itself is expressed as a Tikhonov regularization problem, which allows one to obtain accurate results without detailed knowledge of the involved errors. When the problem is linear and the errors fulfill certain assumptions, the resulting solution is known to be the best linear unbiased estimator. The main objective of this study is to construct a new solution method for fixed-interval smoothing problems; one which can be readily used in practical applications, where detailed knowledge of the involved errors is not available. The proposed solution method is presented in a detailed enough level to be implemented in a high-level environment such as Matlab. Therefore, the thesis also presents a reference implementation of an algorithm designed to solve linear fixed-interval smoothing problems. This thesis concludes by applying the proposed solution method to two sports in which such technology has not been used before

Intermediate ions as a strong indicator of new particle formation bursts in a boreal forest

Secondary aerosol formation from gas-phase precursors is a frequent phenomenon occurring in a boreal environment. Traditionally, this process is identified visually from observational data on total and ion number size distributions. Here, we introduce a new, objective classification method for the new particle formation events based on measured intermediate-ion concentrations. The intermediate-ion concentration is a suitable indicator of new particle formation, because it is linked to the atmospheric new particle formation. The concentration of intermediate ions is typically very low (below 5 cm(-3)) when there is no new particle formation or precipitation events occurring. In this study, we analysed concentrations of negative intermediate ions at the Station for Measuring Ecosystem Atmosphere Relations (SMEAR II) in Hyytiala, Finland, during the years 2003-2013. We found that the half-hour median concentration of negative intermediate ions in sizes 2-4 nm was > 20 cm(-3) during 77.5% of event days classified by traditional method. The corresponding value was 92.3% in the case of 2-7 nm negative ions. In addition, the intermediate-ion concentration varied seasonally in a similar manner as the number of event days, peaking in the spring. A typical diurnal variation of the intermediate-ion concentration resembled that of the particle concentration during the event days. We developed here a new method for classifying new particle formation events based on intermediate-ion concentrations. The new method is complementary to the traditional event analysis and it can also be used as an automatic way of determining new particle formation events from large data sets.Peer reviewe

Impaired WNT signaling and the spine-Heterozygous WNT1 mutation causes severe age-related spinal pathology

Background: WNT signaling plays a major role in bone and cartilage metabolism. Impaired WNT/beta-catenin signaling leads to early-onset osteoporosis, but specific features in bone and other tissues remain inadequately characterized. We have identified two large Finnish families with early-onset osteoporosis due to a heterozygous WNT1 mutation c.652T>G, p.C218G. This study evaluated the impact of impaired WNT/beta-catenin signaling on spinal structures. Methods: Altogether 18 WNT1 mutation-positive (age range 11-76 years, median 49 years) and 14 mutation negative subjects (10-77 years, median 43 years) underwent magnetic resonance imaging (MRI) of the spine. The images were reviewed for spinal alignment, vertebral compression fractures, intervertebral disc changes and possible endplate deterioration. The findings were correlated with clinical data. Results: Vertebral compression fractures were present in 78% (7/9) of those aged over 50 years but were not seen in younger mutation-positive subjects. All those with fractures had several severely compressed vertebrae. Altogether spinal compression fractures were present in 39% of those with a WNT1 mutation. Only 14% (2/14) mutation -negative subjects had one mild compressed vertebra each. The mutation-positive subjects had a higher mean spinal deformity index (4.0 +/- 7.3 vs 0.0 +/- 0.4) and more often increased thoracic kyphosis (Z-score > + 2.0 in 33% vs 0%). Further, they had more often Schmorl nodes (61% vs 36%), already in adolescence, and their intervertebral discs were enlarged. Conclusion: Compromised WNT signaling introduces severe and progressive changes to the spinal structures. Schmorl nodes are prevalent even at an early age and increased thoracic kyphosis and compression fractures become evident after the age of 50 years. Therapies targeting the WNT pathway may be an effective way to prevent spinal pathology not only in those harboring a mutation but also in the general population with similar pathology. (C) 2017 Elsevier Inc. All rights reserved.Peer reviewe

Dynamics of aerosol, humidity, and clouds in air masses travelling over Fennoscandian boreal forests

Boreal forests cover vast areas of land in the high latitudes of the Northern Hemisphere, which are under amplified climate warming. The interactions between the forests and the atmosphere are known to generate a complex set of feedback processes. One feedback process, potentially producing a cooling effect, is associated with an increased reflectance of clouds due to aerosol-cloud interactions. Here, we investigate the effect that the boreal forest environment can have on cloud-related properties during the growing season. The site investigated was the SMEAR II station in Hyytiala, Finland. Air mass back trajectories were the basis of the analysis and were used to estimate the time each air mass had spent over land prior to its arrival at the station. This enabled tracking the changes occurring in originally marine air masses as they travelled across the forested land. Only air masses arriving from the northwestern sector were investigated, as these areas have a relatively uniform forest cover and relatively little anthropogenic interference. We connected the air mass analysis with comprehensive in situ and remote-sensing data sets covering up to 11 growing seasons. We found that the properties of air masses with short land transport times, thereby less influenced by the forest, differed from those exposed to the forest environment for a longer period. The fraction of air masses with cloud condensation nuclei concentrations (at 0.2 % supersaturation) above the median value of 180 cm(-3) of the analysed air masses increased from approximately 10 % to 80 % after 55 h of exposure to boreal forest, while the fraction of air masses with specific humidity above the median value of 5 g kg(-1) increased from roughly 25 % to 65 %. Signs of possible resulting changes in the cloud layer were also observed from satellite measurements. Lastly, precipitation frequency increased from the average of approximately 7 % to about 12 % after a threshold of 50 h of land transport. Most of the variables showed an increase with an increasing land transport time until approximately 50-55 h, after which a balance with little further variation seemed to have been reached. This appears to be the approximate timescale in which the forest-cloud interactions take effect and the air masses adjust to the local forest environment.Peer reviewe

Trends in atmospheric new-particle formation : 16 years of observations in a boreal-forest environment

Peer reviewe

Measurement report : Increasing trend of atmospheric ion concentrations in the boreal forest

The concentration of atmospheric ions affects the total aerosol particle number concentrations in the atmosphere as well as atmospheric new particle formation via ion-induced nucleation, ion-ion recombination, and effects on condensational growth. In this study, we investigate the concentrations and long-term trends of atmospheric ions in a boreal forest environment using 16 years of cluster ion (0.8-2 nm) and intermediate ion (2-7 nm) measurements and characterize the most important factors that explain those trends. We found that the median concentration of cluster ions in a boreal forest was 710 cm(-3), the median concentration of 2-4 intermediate ions was 14 cm(-3), and the median concentration of 4-7 nm intermediate ions was 9 cm(-3). The concentrations of both cluster and intermediate ions have been increasing over the 16-year measurement period, with cluster ion concentrations increasing by about 1 % yr(-1) and intermediate ion concentrations increasing 1.7 %-3.9 % yr(-1). The increase in cluster ion concentrations can be best explained by the decrease in the coagulation sink caused by larger aerosol particles. Meanwhile, the dependence of intermediate ion concentrations on meteorological conditions is evident, but ionization sources and the coagulation sink do not seem to explain the increasing trend. This is likely because the dynamics of intermediate ions are more complicated, so that ionization sources and the coagulation sink alone cannot directly explain the variation. Season-specific analysis of the ion concentrations suggests that while the coagulation sink is the limiting factor for the ion concentrations in spring and summer, the dynamics are different in autumn and winter. Based on our findings, we recommend that a more comprehensive analysis is needed to determine if the increase in ambient ion concentrations, increasing temperature, and changing abundance of condensable vapors makes ion-mediated and ion-induced nucleation pathways in the boreal forest more relevant in the future.Peer reviewe

Measurements of cluster ions using a nano radial DMA and a particle size magnifier in CLOUD

We built a new instrumental setup for measuring ion distributions in the size range [1.3-6] nm. The implementation of an high transmission inlet increased the total transmission efficiency to more than 6% at 1.47 nm mobility equivalent diameter, allowing the detection of ions at atmospheric concentrations. The size resolution of our measurements is as high as 6. We characterized the instrument in the laboratory and carried out measurements during the CLOUD7 campaign. We compared the results obtained with the Neutral cluster and Air Ion spectrometer finding very good agreement

Practical realization of a sub-λ/2 acoustic jet

Studies in optics and acoustics have employed metamaterial lenses to achieve sub-wavelength localization, e.g. a recently introduced concept called 'acoustojet' which in simulations localizes acoustic energy to a spot smaller than lambda/2. However previous experimental results on the acoustojet have barely reached lambda/2-wide localization. Here we show, by simulations and experiments, that a sub-lambda/2 wide localization can be achieved by translating the concept of a photonic jet into the acoustic realm. We performed nano-to macroscale molecular dynamics (MD) and finite element method (FEM) simulations as well as macroscale experiments. We demonstrated that by choosing a suitable size cylindrical lens, and by selecting the speed-of-sound ratio between the lens material(s) and the surrounding medium, an acoustic jet ('acoustic sheet') is formed with a full width at half maximum (FWHM) less than lambda/2. The results show, that the acoustojet approach can be experimentally realized with easy-to-manufacture acoustic lenses at the macroscale. MD simulations demonstrate that the concept can be extended to coherent phonons at nanoscale. Finally, our FEM simulations identify some micrometer size structures that could be realized in practice. Our results may contribute to starting a new era of super resolution acoustic imaging: We foresee that jet generating constructs can be readily manufactured, since suitable material combinations can be found from nanoscale to macroscale. Tight focusing of mechanical energy is highly desirable in e.g. electronics, materials science, medicine, biosciences, and energy harvesting.Peer reviewe

Characteristics of new-particle formation at three SMEAR stations

We analyzed the size distributions of atmospheric aerosol particles measured during 2013-2014 at Varrio (SMEAR I) in northern Finland, Hyytiala (SMEAR II) in southern Finland and Jarvselja (SMEAR-Estonia) in Estonia. The stations are located on a transect spanning from north to south over 1000 km and they represent different environments ranging from subarctic to the hemi-boreal. We calculated the characteristics of new-particle-formation events, such as the frequency of events, growth rate of nucleation mode particles, condensation and coagulation sinks, formation rate of 2 nm and 3 nm particles, and source rate of condensable vapors. We observed 59, 185 and 108 new-particle-formation events at Varrio, Hyytiala and Jarvselja, respectively. The frequency of the observed events showed an annual variation with a maximum in spring. The analysis revealed size dependence of growth rate at all locations. We found that the growth rate and source rate of a condensable vapor were the highest in Jarvselja and the lowest in Varrio. The condensation sink and particle formation rate were of a similar magnitude at Hyytiala and Jarvselja, but several times smaller at Varrio. Tracking the origin of air masses revealed that the number concentration of nucleation mode particles (3-25 nm) varied from north to south, with the highest concentrations at Jarvselja and lowest at Varrio. Trajectory analysis indicated that new-particle-formation events are large-scale phenomena that can take place concurrently at distant stations located even 1000 km apart. We found a total of 26 days with new-particle-formation events occurring simultaneously at all three stations.Peer reviewe

Effect of baseline characteristics on mortality in the SURVIVE trial on the effect of levosimendan vs dobutamine in acute heart failure: Sub-analysis of the Finnish patients

Peer reviewe