Validation of satellite based railway positioning systems

Satellitennavigation ist heutzutage für die Ortungssysteme im Straßen- und Schienenverkehr unumgänglich, trotzdem gibt es zurzeit nur wenige verbreitete Anwendungen. Die aktuellen Arbeiten von Forschungsinstitutionen, Komponentenherstellern, der Eisenbahnindustrie sowie nationalen und internationalen Behörden oder Einrichtungen die sich mit diesem Bereich beschäftigen, zeigen, dass hier ein großes Anwendungspotenzial besteht. Die Eigenschaften und Merkmale dieser Satellitennavigationssysteme wie z.B. die Verfügbarkeit werden stark von den Umgebungsbedingungen beeinflusst, da diese Bedingungen die Stärke und die Ausbreitung der empfangenen Signale beeinträchtigen. Hierbei ist eine ausführliche Analyse der kritischen Szenarien, die diese Umgebungsbedingungen beschreiben, unentbehrlich, um so die Auswirkungen auf die Energie des empfangenen Signals in solchen Umgebungen besser zu verstehen. Auf diese Weise können ggf. die systemspezifischen Merkmale bei der Entwicklung und den Einsatz solcher Systeme berücksichtig werden. In dieser Arbeit werden die wichtigen Aspekte satelliten¬basierter Ortungssysteme erläutert und einige relevante Merkmale sowie ein systematischer Einsatz hergeleitet, die charakteristischen Größen von GNSS mit Hilfe eines unabhängigen Referenzmesssystems zu ermitteln. Es werden die grundlegenden Einsatzmöglichkeiten von Referenzmesssystemen für satellitenbasierte Anwendungen im Eisenbahnbereich diskutiert und schließlich wird auch einer der ersten Ansätze skizziert und erläutert. Dazu wird auch das resultierende Referenzmesssystem vorgestellt und erläutert. Mit diesen werden während einer Testfahrt Daten entsprechend einem Testszenario erhoben. Die Positionsungenauigkeit für statische und dynamische Messungen wird mittels des Referenzmesssystems („GaTRail“) verglichen und anschließend analysiert. So wird gezeigt, dass man während der dynamischen Messungen (bei Berücksichtigung minimaler Umgebungs-eigenschaften) einige wichtige Eigenschaften GNSS basierter Positionsbestimmung quantitativ und qualitativ betrachtet kann. Schließlich wird das zugehörige Messmanagementsystem beschrieben und einige allgemeine sowie spezifische Anforderungen werden aufgelistet. Abschließend wird der gesamte Themen¬bereich in den Kontext Validierung von GNSS basierten Anwendungen eingeordnet, der Teil eines Zertifizierungsprozesses ist. Dieser wird zusammen mit einem erforderlichen dem Akkreditierungsprozess formal dargestellt und erläutert.Nowadays, satellite navigation is widespread for positioning systems in road and railway traffic, yet there are presently few prevalent applications. Current workings of research institutions, manufacturers of components, railway industry as well as national and interna-tional authorities or institutions dealing with this domain show actually that a huge application potential does exist. These satellite navigation systems’ main parameters, e.g. their availability are strongly affected by environmental conditions, as these conditions have an effect on the received signals. Here it is indispensable to perform a thorough analysis of critical scenarios describing the environmental conditions, in order to obtain a better understanding of the impact on the performance of the received signal in these environments. In doing so, it is possible to take the characteristics specific for the system into consideration during development and use. This work will illustrate the important aspects of satellite-based positioning systems and describe some of the relevant characteristics in detail. It discusses the basic possibilities of application of reference measuring systems for satellite-based applications in railway traffic and will finally give an outline of and explain one of the first approaches. During a test drive, data are gathered according to a test scenario. The positioning inaccuracy of static and dynamic measurements will be compared using the reference measuring system “GaTRail”, and analyzed subsequently. This will show that it is possible to consider numerous important features of GNSS-based location determination during dynamic measurements quantitatively and qualitatively (considering a minimal GNSS reception condition). Finally, the measurement management system will be described, and some general as well as specific requirements will be listed. The entire work deals with the subject “Validation of GNSS-based applications” which is part of a certification process. The latter will be formally described and explained

ToyArchitecture: Unsupervised Learning of Interpretable Models of the World

Research in Artificial Intelligence (AI) has focused mostly on two extremes: either on small improvements in narrow AI domains, or on universal theoretical frameworks which are usually uncomputable, incompatible with theories of biological intelligence, or lack practical implementations. The goal of this work is to combine the main advantages of the two: to follow a big picture view, while providing a particular theory and its implementation. In contrast with purely theoretical approaches, the resulting architecture should be usable in realistic settings, but also form the core of a framework containing all the basic mechanisms, into which it should be easier to integrate additional required functionality. In this paper, we present a novel, purposely simple, and interpretable hierarchical architecture which combines multiple different mechanisms into one system: unsupervised learning of a model of the world, learning the influence of one's own actions on the world, model-based reinforcement learning, hierarchical planning and plan execution, and symbolic/sub-symbolic integration in general. The learned model is stored in the form of hierarchical representations with the following properties: 1) they are increasingly more abstract, but can retain details when needed, and 2) they are easy to manipulate in their local and symbolic-like form, thus also allowing one to observe the learning process at each level of abstraction. On all levels of the system, the representation of the data can be interpreted in both a symbolic and a sub-symbolic manner. This enables the architecture to learn efficiently using sub-symbolic methods and to employ symbolic inference.Comment: Revision: changed the pdftitl

Altered potassium channel distribution and composition in myelinated axons suppresses hyperexcitability following injury

Neuropathic pain following peripheral nerve injury is associated with hyperexcitability in damaged myelinated sensory axons, which begins to normalise over time. We investigated the composition and distribution of shaker-type-potassium channels (Kv1 channels) within the nodal complex of myelinated axons following injury. At the neuroma that forms after damage, expression of Kv1.1 and 1.2 (normally localised to the juxtaparanode) was markedly decreased. In contrast Kv1.4 and 1.6, which were hardly detectable in the naïve state, showed increased expression within juxtaparanodes and paranodes following injury, both in rats and humans. Within the dorsal root (a site remote from injury) we noted a redistribution of Kv1-channels towards the paranode. Blockade of Kv1 channels with α-DTX after injury reinstated hyperexcitability of A-fibre axons and enhanced mechanosensitivity. Changes in the molecular composition and distribution of axonal Kv1 channels, therefore represents a protective mechanism to suppress the hyperexcitability of myelinated sensory axons that follows nerve injury

Animal models of episodic ataxia type 1 (EA1)

Episodic ataxia type 1 (EA1) is an autosomal dominant neurological disorder characterized by myokymia and attacks of ataxic gait often precipitated by stress. Several genetic mutations have been identified in the Shaker-like K+ channel Kv1.1 (KCNA1) of individuals with EA1. K+ channels are membrane proteins that allow the selected and concerted movement of K+ across a cell membrane that is otherwise relatively impermeable. Voltage-gated K+ channels shorten the duration of action potentials and control the excitability of central and peripheral neurons. EA1 is classified among ion channel diseases known as channelopathies (CPs). To date, a large group of CPs has been identified and new ones are continuously discovered. They result in a very diverse class of diseases ranging from ataxia, epilepsy, migraine, and psychiatric disorders to dysfunction of the skeletal muscle, kidney, and endocrinology system. Certainly, research using animal models of EA1 is providing important knowledge concerning the signaling pathways and circuits involved in this disease and in finding novel pharmacological interventions to ameliorate the symptoms. More broadly, investigations of CPs at the molecular and whole-animal levels will help further our understanding of the functional properties of ion channels and, eventually, the physiological workings of the human body.peer-reviewe

Claudin 13, a Member of the Claudin Family Regulated in Mouse Stress Induced Erythropoiesis

Mammals are able to rapidly produce red blood cells in response to stress. The molecular pathways used in this process are important in understanding responses to anaemia in multiple biological settings. Here we characterise the novel gene Claudin 13 (Cldn13), a member of the Claudin family of tight junction proteins using RNA expression, microarray and phylogenetic analysis. We present evidence that Cldn13 appears to be co-ordinately regulated as part of a stress induced erythropoiesis pathway and is a mouse-specific gene mainly expressed in tissues associated with haematopoietic function. CLDN13 phylogenetically groups with its genomic neighbour CLDN4, a conserved tight junction protein with a putative role in epithelial to mesenchymal transition, suggesting a recent duplication event. Mechanisms of mammalian stress erythropoiesis are of importance in anaemic responses and expression microarray analyses demonstrate that Cldn13 is the most abundant Claudin in spleen from mice infected with Trypanosoma congolense. In mice prone to anaemia (C57BL/6), its expression is reduced compared to strains which display a less severe anaemic response (A/J and BALB/c) and is differentially regulated in spleen during disease progression. Genes clustering with Cldn13 on microarrays are key regulators of erythropoiesis (Tal1, Trim10, E2f2), erythrocyte membrane proteins (Rhd and Gypa), associated with red cell volume (Tmcc2) and indirectly associated with erythropoietic pathways (Cdca8, Cdkn2d, Cenpk). Relationships between genes appearing co-ordinately regulated with Cldn13 post-infection suggest new insights into the molecular regulation and pathways involved in stress induced erythropoiesis and suggest a novel, previously unreported role for claudins in correct cell polarisation and protein partitioning prior to erythroblast enucleation

Driver Response Time and Age Impact on the Reaction Time of Drivers: A Driving Simulator Study among Professional-Truck Drivers

Drivers' response time means that drivers act after a judgment is made when an emergency action signal is needed. Drivers have different feelings while driving, and the response time to sudden situations differs. The main purpose of this study was to verify whether the mean reaction time of professional drivers is at the level of one second, which is the value usually used for practical purposes, and to verify the impact of age on the reaction times of drivers. Two different studies with a total of 120 participants-professional drivers-were conducted on the simulator, with 116 drivers participating in the first experiment and four drivers participating in the second experiment using eye-tracking technology. The determination of the mean reaction time was realized using statistical tests. The evaluation of the impact of age on the reaction time of professional drivers was carried out using statistical testing, a regression model, and clustering. The results of this study can be immediately used in practice for professional drivers, as the mean reaction time is usually used as a benchmark in several calculations in transport, for forensic and educational purposes, and for planning traffic and modelling different traffic situations