Road Friction Estimation for Connected Vehicles using Supervised Machine Learning

In this paper, the problem of road friction prediction from a fleet of connected vehicles is investigated. A framework is proposed to predict the road friction level using both historical friction data from the connected cars and data from weather stations, and comparative results from different methods are presented. The problem is formulated as a classification task where the available data is used to train three machine learning models including logistic regression, support vector machine, and neural networks to predict the friction class (slippery or non-slippery) in the future for specific road segments. In addition to the friction values, which are measured by moving vehicles, additional parameters such as humidity, temperature, and rainfall are used to obtain a set of descriptive feature vectors as input to the classification methods. The proposed prediction models are evaluated for different prediction horizons (0 to 120 minutes in the future) where the evaluation shows that the neural networks method leads to more stable results in different conditions.Comment: Published at IV 201

Efficacy of Phlebiopsis gigantea treatment on spore infections of Heterobasidion spp. on Larix X eurolepis

The effectiveness of Phlebiopsis gigantea to prevent spore infections from Heterobasidion annosum and Heterobasidion parviporum on hybrid larch stumps were investigated in five stands in southern Sweden. All sites are former forest land and the age of the trees was between 9 and 13 years. The study was implemented in August 2010, a month where spore dispersal should be great. The five sites were located in previously un‐thinned monocultures of hybrid larch. The spore load in the air was studied with the help of spore traps from three different tree species; Norway spruce, Scots pine and hybrid larch. A total of 146 spore traps, evenly distributed in all five sites were analyzed. The spore traps were exposed for three hours then brought back to the laboratory for incubation and analysis. The hybrid larch trees were randomly selected, cut down and every second stump was treated with Rotstop® S and the others were left as controls. No visible signs of infections were discovered. Roughly 60 days after felling and treatment, disc samples were collected for further analysis in lab. The study indicates an abundant amount of basidiospores of Heterobasidion spp. in the air. 63,7 % of all spore traps was infected with Heterobasidion spp. Most infections were found in Södra Rörum II, with 83 % infected spore traps. Out of 263 colonies, 61,2 % of the isolations were infections of H. annosum and 38,8 % were H. parviporum. Scots pine and hybrid larch were most attacked by H. annosum whilst Norway spruce was equally attacked by H. annosum and H. parviporum. The mean percentage of infected stumps for all five sites per tree species was; larch 52 %, Norway spruce 58 % and Scots pine 72 %. A total of 176 hybrid larch stumps were analyzed and 20 % were infected by Heterobasidion spp. Both H. annosum and H. parviporum were isolated from the hybrid larch stumps. 60 % of the isolations were H. parviporum and 40 % were H. annosum. Highest infection rate was found in Fulltofta and Klippan where 24 % of the stumps were infected. There is a significant difference of infection rate and infected area between treated stumps and un‐treated control stumps, where p < 0,000 and p < 0,024 respectively. This result makes Rotstop® S an interesting stump treatment alternative also on hybrid larch

Polisens rättsmedvetande

Den här uppsatsens syfte är att beskriva en grupp ungdomspolisers rättsmedvetande samt syn på straffens preventiva förmågor. Detta görs utifrån en allmänuppfattning om att polisen har ett konservativt synsätt på straff mot bakgrund av kriminologisk litteratur. Frågeställningen lyder: Hur är dessa polisers rättsmedvetande och finns det en skillnad mot den gängse bilden. Hur ser polisen på straffen preventiva förmågor. Uppsatsens utgångspunkt är att undersöka om den gängse bilden av poliser som hårda och konservativa då det kommer till straff verkligen stämmer. Jag gjorde en kvalitativ intervjustudie av fem ungdomspoliser i en medelstor stad där varje intervju var på ungefär en timme. Det jag dock kom fram till var att åtminstone de poliser jag intervjuat inte har den här typiska hårda synen på brott och straff. De är snarare benägna att se bakgrundsfaktorer till brottslighet samt ser de varje kriminell som individ och skulle utifrån det se ett mer individualiserat straffsystem som utgick mer ifrån den kriminelles återanpassning än ett allmänpreventivt straffande

High-Current GaSb/InAs(Sb) Nanowire Tunnel Field-Effect Transistors

We present electrical characterization of GaSb/InAs(Sb) nanowire tunnel field-effect transistors. The broken band alignment of the GaSb/InAs(Sb) heterostructure is exploited to allow for interband tunneling without a barrier, leading to high ON-current levels. We report a maximum drive current of 310 μA/μm at Vds = 0.5 V. Devices with scaled gate oxides display transconductances up to gm = 250 mS/mm at Vds = 300 mV, which are normalized to the nanowire circumference at the axial heterojunction

Modulating Surrogates for Bayesian Optimization

Bayesian optimization (BO) methods often rely on the assumption that the objective function is well-behaved, but in practice, this is seldom true for real-world objectives even if noise-free observations can be collected. Common approaches, which try to model the objective as precisely as possible, often fail to make progress by spending too many evaluations modeling irrelevant details. We address this issue by proposing surrogate models that focus on the well-behaved structure in the objective function, which is informative for search, while ignoring detrimental structure that is challenging to model from few observations. First, we demonstrate that surrogate models with appropriate noise distributions can absorb challenging structures in the objective function by treating them as irreducible uncertainty. Secondly, we show that a latent Gaussian process is an excellent surrogate for this purpose, comparing with Gaussian processes with standard noise distributions. We perform numerous experiments on a range of BO benchmarks and find that our approach improves reliability and performance when faced with challenging objective functions

Compositional Uncertainty in Deep Gaussian Processes

Gaussian processes (GPs) are nonparametric priors over functions. Fitting a GP implies computing a posterior distribution of functions consistent with the observed data. Similarly, deep Gaussian processes (DGPs) should allow us to compute a posterior distribution of compositions of multiple functions giving rise to the observations. However, exact Bayesian inference is intractable for DGPs, motivating the use of various approximations. We show that the application of simplifying mean-field assumptions across the hierarchy leads to the layers of a DGP collapsing to near-deterministic transformations. We argue that such an inference scheme is suboptimal, not taking advantage of the potential of the model to discover the compositional structure in the data. To address this issue, we examine alternative variational inference schemes allowing for dependencies across different layers and discuss their advantages and limitations.Comment: 17 page