Anthony C. Davies

Image Processing Techniques for Crowd Density Estimation Using a Reference Image

There are still significant problems in the planning, design and management of public facilities subject to dense pedestrian traffic. The automation of data collection and analysis of crowd behaviour is increasingly desirable in design of facilities and long-term site management using image processing techniques with existing closed-circuit television systems. We have investigated a number of techniques for crowd density estimation, movement estimation, incident detection and their relative merits using image processing. This paper presents techniques for background generation and calibration to enhance the previously-developed method of crowd density estimation using a reference image. An intensity region related to the average pixel intensity of each image in a sequence of crowd images is used to segment background pixels for generating a background image without pedestrians. The calibration approach, with which a previously-established relationship between image parameters and crowd density at one site can be used to estimate crowd density at various sites, involves calibration of the crowd image as opposed to calibration of the camera. Both techniques may be used in other surveillance systems such as vehicle monitoring.

Nonlinear Oscillations and Chaos from Digital Filter Overflow

Nonlinear digital-filter overflow-oscillations arising from two’s complement arithmetic are described with the emphasis on explaining the reasons for the behaviour and providing illustrations of typical oscillations. The complex properties of some of these oscillations have led to extensive investigations of the nonlinear dynamics and to proposals for applications. The paper provides an introduction to the published literature on this subject.

Chaotic signals generated by digital filter overflow

The paper surveys the chaotic behaviour of digital filter overflow oscillations. The behaviour patterns of 1st, 2nd and 3rd order filters are described and the available stochastic characteristics of oscillations with chaotic features are illustrated by means of probability density functions and power density spectra for a range of filter parameters and initial states. The analysis and simulation results provide a basis for the design of digital systems which generate signals with a variety of prescribed characteristics. Typical examples are included.<<ETX>>

Geometrical analysis of digital-filter overflow oscillations

The large-amplitude oscillations that can occur in recursive digital filters as a result of the overflow-characteristic of twos complement arithmetic are analyzed by a geometrical approach that is shown to provide a straightforward and convenient method of deriving some general and analytical results. In particular, conditions for the existence of certain classes of overflow oscillation are obtained, with analytical expressions for states that initiate them.<<ETX>>

Evaluation of the Data Interaction Architecture Demonstrator by means of a multiple mobile robot workspace simulation

Abstract This paper gives an introduction to the Data Interaction Architecture Demonstrator (DIADEM) designed and built by British Aerospace Dynamics, and describes an example of the use of the Demonstrator for a multiple-robot workspace simulation. The design method, the hardware and the software for DIADEM are outlined, followed by a discussion of the strategy and algorithms used for the simulation. Some comparisons with alternative strategies for the simulation are made.

A parallel simulation of multiple mobile robots using the DORIS design method

This paper introduces the data oriented requirements implementation scheme (DORIS) design strategy and the data interaction architecture demonstrator (DIADEM), by describing their use for a multiple-robot workspace simulation. The design process, the hardware and the software for the DIADEM are outlined, followed by a discussion of the design used for the simulation.<<ETX>>

Decision points in career and life: being a volunteer

During life there are decision points which can dramatically influence the future direction of our lives. Unlike typical scientific experiments there is no possibility to re-run the experiences and discover the result of making a different decision, so only speculation is available. After a discussion of the framework of these decision points, the author relates them to his own experiences as a volunteer, mainly in IEEE, and describes some opportunities which these created for him. It is based on a presentation given at an IEEE Student Branch event at University of Bath [1].

Research: Design principles and performance for flooding routing mesh topology spread spectrum LANs

This paper presents a family of mesh topology LANs that uses spread spectrum techniques as a method for media access control so as to offer (1) the possibility of simultaneous access to the network, and (2) to provide similar performance to all communication channels while reducing the probability of any collision. For routing, flooding algorithms are proposed. The proposed architecture is characterized by survivability, security and relatively low bandwidth requirements. A LAN member of this family is also analysed. It is built on a topology that consists of a set of inter-communicating sub-LANs and interconnected subgraphs. The topology, the communication and the signalling protocols that support this architecture are presented. Parameters influencing the traffic load of such a LAN are examined, and estimates of the bit error rate (BER) as a function of the parameters are presented.