On Optimal Binary One-Error-Correcting Codes of Lengths 2m−42^m-4 and 2m−32^m-3

Best and Brouwer [Discrete Math. 17 (1977), 235-245] proved that triply-shortened and doubly-shortened binary Hamming codes (which have length $2^m-4$ and $2^m-3$, respectively) are optimal. Properties of such codes are here studied, determining among other things parameters of certain subcodes. A utilization of these properties makes a computer-aided classification of the optimal binary one-error-correcting codes of lengths 12 and 13 possible; there are 237610 and 117823 such codes, respectively (with 27375 and 17513 inequivalent extensions). This completes the classification of optimal binary one-error-correcting codes for all lengths up to 15. Some properties of the classified codes are further investigated. Finally, it is proved that for any $m \geq 4$, there are optimal binary one-error-correcting codes of length $2^m-4$ and $2^m-3$ that cannot be lengthened to perfect codes of length $2^m-1$.Comment: Accepted for publication in IEEE Transactions on Information Theory. Data available at http://www.iki.fi/opottone/code

The factors of motion sickness:developing Janitor Run, the virtual reality scooter game

Abstract. This bachelor’s thesis presents a study on the effects of motion sickness, vection and nausea in the context of virtual reality environments through a developed virtual reality kick scooting game called Janitor Run VR. The main research problems to be studied were which of the many aspects of virtual reality games induce motion sickness and nausea, and how these negative effects can be mitigated or eliminated. The methods used were twofold. First, a brief literature review was conducted on the history, best practices and common problems on virtual reality. Then, a two-phased evaluation was conducted, where participants were asked to try the developed game and give feedback on the studied negative effects through an interview and a questionnaire. The results gathered from 12 different participants on each evaluation phase seem to indicate, that there is a link between the perceived discomfort and motion sickness with a more realistic motion scheme and the use of sound effects and background music.Matkapahoinvoinnin tekijät : virtuaalitodellisuuspotkulautailupelin, Janitor Runin, kehittäminen. Tiivistelmä. Tämä kandidaatintyö tuo esille tutkimuksen matkapahoinvointiin ja vektion virtuaalitodellisuudessa kehitetyn virtuaalitodellisuuspotkulautapelin, Janitor Run VR:n, kautta. Kandidaatintyön päätutkimusongelmat käsittelevät sitä, kuinka virtuaalitodellisuuspelit saavat aikaan pahoinvointia ja kuinka niiden haitallisia vaikutuksia voidaan vähentää tai eliminoida. Tutkimuksessa käytettiin kahta tutkimusmenetelmää. Ensin suoritettiin lyhyt kirjallisuuskatsaus virtuaalitodellisuuden historiasta, parhaista käytäntötavoista sekä yleisistä ongelmista. Sen jälkeen toisena menetelmänä käytettiin kaksivaiheista evaluaatiota, joissa molemmissa kerättiin palautetta 12 osallistujilta tutkittuihin negatiivisiin vaikutuksiin haastattelun ja kyselyn avulla. Tutkimuksen tulokset näyttävät osoittavan linkin havaitun pahoinvoinnin, realistisen liikkumisen sekä äänitehosteiden ja taustamusiikin kanssa

Effects of Spatial Dispersion on Reflection from Mushroom-type Artificial Impedance Surfaces

Several recent works have emphasized the role of spatial dispersion in wire media, and demonstrated that arrays of parallel metallic wires may behave very differently from a uniaxial local material with negative permittivity. Here, we investigate using local and non-local homogenization methods the effect of spatial dispersion on reflection from the mushroom structure introduced by Sievenpiper. The objective of the paper is to clarify the role of spatial dispersion in the mushroom structure and demonstrate that under some conditions it is suppressed. The metamaterial substrate, or metasurface, is modeled as a wire medium covered with an impedance surface. Surprisingly, it is found that in such configuration the effects of spatial dispersion may be nearly suppressed when the slab is electrically thin, and that the wire medium can be modeled very accurately using a local model. This result paves the way for the design of artificial surfaces that exploit the plasmonic-type response of the wire medium slab.Comment: submitted for publication, under revie

Experiments on Vortices in Rotating Superfluid 3He-A

A satellite peak has been observed in the NMR spectrum of rotating 3He-A; the peak intensity depends linearly on Ω at the high angular velocities, Ω=0.6−1.5 rad/s, needed to resolve it. The frequency shift of the satellite is independent of Ω. These results strongly suggest the existence of vortices in rotating 3He-A with the vortex density proportional to Ω. Another satellite peak also has been observed which probably is due to solitons.Peer reviewe

The effects of drainage and restoration of pine mires on habitat structure, vegetation and ants

Habitat loss and degradation are the main threats to biodiversity worldwide. For example, nearly 80% of peatlands in southern Finland have been drained. There is thus a need to safeguard the remaining pristine mires and to restore degraded ones. Ants play a pivotal role in many ecosystems and like many keystone plant species, shape ecosystem conditions for other biota. The effects of mire restoration and subsequent vegetation succession on ants, however, are poorly understood. We inventoried tree stands, vegetation, water-table level, and ants (with pitfall traps) in nine mires in southern Finland to explore differences in habitats, vegetation and ant assemblages among pristine, drained (30-40 years ago) and recently restored (1-3 years ago) pine mires. We expected that restoring the water-table level by ditch filling and reconstructing sparse tree stands by cuttings will recover mire vegetation and ants. We found predictable responses in habitat structure, floristic composition and ant assemblage structure both to drainage and restoration. However, for mire-specialist ants the results were variable and longer-term monitoring is needed to confirm the success of restoration since these social insects establish perennial colonies with long colony cycles. We conclude that restoring the water-table level and tree stand structure seem to recover the characteristic vegetation and ant assemblages in the short term. This recovery was likely enhanced because drained mires still had both acrotelm and catotelm, and connectedness was still reasonable for mire organisms to recolonize the restored mires either from local refugia or from populations of nearby mires.Peer reviewe

Free energy principle inspired image recognition with convolutional neural networks

Abstract. Since its inception, the field of neuroscience has studied the way the human brain perceives and learns about its environment. Several theories have been created in an effort to understand these phenomena and few have garnered as much interest as Karl Friston’s free energy principle (FEP). The free energy principle states that any self-organizing system that is at equilibrium with its environment must minimize its free energy. The principle is essentially a mathematical formulation of how adaptive systems (that is, biological agents, like animals or brains) resist a natural tendency to disorder. Friston’s principle provides a framework that explains not only how the brain functions, but how any stable system organizes itself. Unsurprisingly a theory of this magnitude has created a lot of debate and received fair share of criticism. Whether or not Friston’s principle is correct or not, it has been proven to be a functional framework in the context of machine learning. The goal of this thesis is to provide an example of a practical implementation of the FEP in the form of a Bayesian Neural Network (BNN), execute image classification on it, and compare its performance to another neural network, Convolutional Neural Network (CNN). Both of these networks are trained with a few different datasets and we are comparing the accuracies and training times of these networks. We begin with an introduction to the key concepts that will help the reader to better understand the topic of this paper. We then present some related work on this topic and continue to introduce the architecture of the CNN and BNN models. In the subsequent section we showcase the results of the training for both the BNN and the CNN. We also provide an analysis of the results of the thesis and discuss possible future work. The final conclusions section contains a summary of the project. The results from the experiments suggest that a CNN is overall more accurate in classifying images. This does not mean that a BNN is useless since the BNN can express uncertainty which is something a CNN is incapable of

Selection for novel, acid-tolerant Desulfovibrio spp. from a closed Transbaikal mine site in a temporal pH- gradient bioreactor

Almost all the known isolates of acidophilic or acid-tolerant sulphate-reducing bacteria (SRB) belong to the spore-forming genus Desulfosporosinus in the Firmicutes. The objective of this study was to isolate acidophilic/acid-tolerant members of the genus Desulfovibrio belonging to deltaproteobacterial SRB. The sample material originated from microbial mat biomass submerged in mine water and was enriched for sulphate reducers by cultivation in anaerobic medium with lactate as an electron donor. A stirred tank bioreactor with the same medium composition was inoculated with the sulphidogenic enrichment. The bioreactor was operated with a temporal pH gradient, changing daily, from an initial pH of 7.3 to a final pH of 3.7. Among the bacteria in the bioreactor culture, Desulfovibrio was the only SRB group retrieved from the bioreactor consortium as observed by 16S rRNA-targeted denaturing gradient gel electrophoresis. Moderately acidophilic/acid-tolerant isolates belonged to Desulfovibrio aerotolerans - Desulfovibrio carbinophilus - Desulfovibrio magneticus and Desulfovibrio idahonensis - Desulfovibrio mexicanus clades within the genus Desulfovibrio. A moderately acidophilic strain, Desulfovibrio sp. VK (pH optimum 5.7) and acid-tolerant Desulfovibrio sp. ED (pH optimum 6.6) dominated in the bioreactor consortium at different time points and were isolated in pure cultur