Implementation and evaluation of wearable reaction time tests

Conducting cognitive assessment tests throughout normal daily life offers new opportunities to early detect changes in cognitive efficiency. Such tests would allow identification of early symptoms of cognitive impairment, monitor the progress of disease processes related to cognitive efficiency and reduce the risk of cognitive overload. Reaction time tests are known as simple and sensitive tests for detecting variation in cognitive efficiency. A drawback of existing reaction time tests is that they require the full attention of a test person, which prohibits the measurement of cognitive efficiency during daily routine tasks. In this contribution we present the design, implementation and empirical evaluation of two wearable reaction time tests that can be operated throughout everyday life. We designed and implemented wearable watch-like devices, which combine the generation of haptic stimuli and the recognition of hand gestures as the subject’s response. For the evaluation of the wearable interface, we conducted a user study with 20 subjects to investigate to what extent we can measure changes in length and variability of user’s reaction time with the wearable interfaces in comparison to well accepted, traditional desktop-based tests. Based on the achieved statistical results, we conclude that the presented wearable reaction time tests are suitable to measure factors that influence length and variability of reaction times.     

Weathering indicator for artificial and natural weathering of wood coatings

The aim of the present study was to find and develop a sensor to evaluate the weathering rates of wood coatings during natural and artificial weathering using a material of known and controlled rate of decomposition. This was achieved by the use of a coating based on poly (vinyl acetate) copolymer binder in combination with Fe²⁺ as redox catalyst. It was possible to model the decomposition rates by dry film thickness, Fe²⁺ concentration and addition of pigments. One application of this sensor for wood coatings is to indicate the need of maintenance.     

Continuous activity recognition in a maintenance scenario: combining motion sensors and ultrasonic hands tracking

We describe the design and evaluation of pattern analysis methods for the recognition of maintenance-related activities. The presented work focuses on the spotting of subtle hand actions in a continuous stream of data based on a combination of body-mounted motion sensors and ultrasonic positioning. The spotting and recognition approach is based on three core ideas: (1) the use of location information to compensate for the ambiguity of hand motions, (2) the use of motion data to compensate for the slow sampling rate and unreliable signal of the low cost ultrasonic positioning system, and (3) an incremental, multistage spotting methodology. The proposed methods are evaluated in an elaborate bicycle repair experiment containing nearly 10 h of data from six subjects. The evaluation compares different strategies and system variants and shows that precision and recall rates around 90% can be achieved.     

How to achieve consistency for 3D city models

Consistency is a crucial prerequisite for a large number of relevant applications of 3D city models, which have become more and more important in GIS. Users need efficient and reliable consistency checking tools in order to be able to assess the suitability of spatial data for their applications. In this paper we provide the theoretical foundations for such tools by defining an axiomatic characterization of 3D city models. These axioms are effective and efficiently supported by recent spatial database management systems and methods of Computational Geometry or Computer Graphics. They are equivalent to the topological concept of the 3D city model presented in this paper, thereby guaranteeing the reliability of the method. Hence, each error is detected by the axioms, and each violation of the axioms is in fact an error. This property, which is proven formally, is not guaranteed by existing approaches. The efficiency of the method stems from its locality: in most cases, consistency checks can safely be restricted to single components, which are defined topologically. We show how a 3D city model can be decomposed into such components which are either topologically equivalent to a disk, a sphere, or a torus, enabling the modeling of the terrain, of buildings and other constructions, and of bridges and tunnels, which are handles from a mathematical point of view. This enables a modular design of the axioms by defining axioms for each topological component and for the aggregation of the components. Finally, a sound, consistent concept for aggregating features, i.e. semantical objects like buildings or rooms, to complex features is presented.     

Notruf 110/112: Notstrom für Notrufe und Anforderungen an IP-Netze

Kann ein Notruf auch bei Stromausfall abgesetzt werden? Müssen schon heute Notrufe aus IP-Netzen ermöglicht werden? Der folgende Artikel diskutiert die zugrunde liegenden Sachverhalte aus rechtlicher und technischer Sicht und gibt Antworten auf die beiden vielfach gestellten Fragen.