Christoph Schierz

Contact-free measurement of heart rate, respiration rate, and body movements during sleep

We describe a noncontact method for the ambulant measurement of basic sleep physiology parameters in humans, particularly for field studies involving sleep research and sleep disturbances. This method traces the body movements, respiration, and heart action of a person at rest or asleep on a bed, using four high-resolution force sensors installed under the bedposts. The recoil movement of the body at each heartbeat, known as the cardioballistic effect, as well as the lifting and lowering of the thorax, while breathing, causes very small shifts of the center of gravity of the bed and the subject. These shifts are reflected in the altering force distributions across the four sensors. Cardiac and respiratory parameters and the subject’s movement activity can be calculated from the sensor signals. Neither electrodes nor other kinds of transducers are in direct contact with the subject, which is the main advantage of this technique over conventional methods. Laboratory experiments were carried out to estimate validity and practicability. The method has been found to be adequate, especially for automated and unattended sleep-data collection over long periods of time.

Algorithm 781: generating Hilbert's space-filling curve by recursion

An efficient algorithm for the generation of Hilberts space-filling curve is given. The algorithm implements a recursive procedure that involves simple integer operations and quickly converges to the set of points that make the Hilbert curve. The algorithm is elegant, short, and considerably easier to implement than previous recursive and nonrecursive algorithms and can be efficiently implemented in all programming languages that have integer operations and allow recursion. The fundamental Hilbert shape (a line joining the four corners of a square) is represented by two variables with values of either 0 or 1. This coding technique could be successfully applied to the generation of other regular space-filling curves, such as the Peano curve.

Annoyance responses to stable and changing aircraft noise exposure

This article reports the two extensive aircraft noise annoyance surveys subsequently carried out among residents in the vicinity of Zurich Airport in 2001 and 2003 in order to update and validate existing exposure-effect relationships for aircraft noise and annoyance in Switzerland. Logistic and polynomial approximations of the exposure-annoyance relationships for both the years 2001 and 2003 are presented for the L(dn), L(den), and L(A,eq24) noise metrics. The results confirm other recently published international research and provide further evidence that community annoyance due to aircraft noise has increased over the past decades. Between the two survey years, a considerable amount of early morning and late evening flight operations have been relocated to use an other runway than before; thus both the effects of a recent step decrease and recent step increase on the exposure-annoyance relationship could be investigated. Residents that experienced a step increase elicited a quite pronounced over-reaction of annoyance which correlated with the magnitude of the change. Two logistic regression models are provided to forecast the effects of changes in exposure during shoulder hours in the early morning and the late evening.

The Effect of the Interface on Learning Style in a Simulation-Based Learning Situation

The applicability of a cognitive theory of implicit and explicit learning to computer-aided learning was tested with a two-factor experimental design. The interface factor tested whether a direct manipulation and a command-based interface can induce the users to implicit or explicit learning, respectively. The complexity factor tested whether the benefit of using one of the interfaces (i.e., learning modes) depends on the task complexity (high or low). According to the theory, the success of using one of the learning modes depends on characteristics of the tasks. The application of the theory to computer-aided learning would be to characterize the learning task and then choose the interface that best fits the task requirements. The ability of the user interfaces to induce the learning modes was supported by the results. The explicit learning mode observed in the users of the command-based interface resulted in better performance for both complexity conditions. Although the users of the direct manipulation...