The influence of visual flow and perceptual load on locomotion speed

Visual flow is used to perceive and regulate movement speed during locomotion. We assessed the extent to which variation in flow from the ground plane, arising from static visual textures, influences locomotion speed under conditions of concurrent perceptual load. In two experiments, participants walked over a 12-m projected walkway that consisted of stripes that were oriented orthogonal to the walking direction. In the critical conditions, the frequency of the stripes increased or decreased. We observed small, but consistent effects on walking speed, so that participants were walking slower when the frequency increased compared to when the frequency decreased. This basic effect suggests that participants interpreted the change in visual flow in these conditions as at least partly due to a change in their own movement speed, and counteracted such a change by speeding up or slowing down. Critically, these effects were magnified under conditions of low perceptual load and a locus of attention near the ground plane. Our findings suggest that the contribution of vision in the control of ongoing locomotion is relatively fluid and dependent on ongoing perceptual (and perhaps more generally cognitive) task demands

Effective security requirements analysis: HAZOP and use cases

Abstract. Use cases are widely used for functional requirements elicitation. However, security non-functional requirements are often neglected in this requirements analysis process. As systems become increasingly complex current means of analysis will probably prove ineffective. In the safety domain a variety of effective analysis techniques have emerged over many years. Since the safety and security domains share many similarities, various authors have suggested that safety techniques might usefully find application in security. This paper takes one such technique, HAZOP, and applies it to one widely used functional requirement elicitation component, UML use cases, in order to provide systematic analysis of potential security issues at the start of system development

Discrete-time sliding mode control on a flexible truss structure

Implementation of discrete-time sliding mode control on a sampled-data system leads to sliding motion in an O(T-2) boundary layer of the discontinuity surface, where T is the sampling period. A truss panel structure vibration control experiment is conducted to demonstrate the effectiveness of the proposed method. This paper utilizes a truncated model to characterize the models of interest and treats all the high frequency modes as disturbances. The experiment includes system identification, state observer design, and discrete-time sliding mode control

Evolution of Digital Filters Using a Gate Array Model

. The traditional paradigm for digital filter design is based on the concept of a linear difference equation with the output response being a weighted sum of signal samples with usually floating point coefficients. Unfortunately such a model is necessarily expensive in terms of hardware as it requires many large bit additions and multiplications. In this paper it is shown how it is possible to evolve a small rectangular array of logic gates to perform low pass FIR filtering. The circuit is evolved by assessing its response to digitised pure sine waves. The evolved circuit is demonstrated to possess nearly linear properties, which means that it is capable of filtering composite signals which it has never seen before. 1 Introduction The difference equation is a fundamental concept employed in the construction and analysis of digital filters [8]. Formally this is represented in the following way. The output of the filter at time n, y(n), may be a function of N samples of the signal x(n-i..