Design for older and disabled people – where do we go from here?

The significant changes in the social, legal, demographic, and economic landscape over the past 10–15 years present enormous opportunities for the human–computer interface design community. These changes will have a significant impact on the design and development of systems for older and disabled people. This paper brings together a number of proposals to improve both specialist and mainstream design methods in the field as a contribution to the debate about design for older and disabled people and the concept of universal usability. Published online: 6 November 2002     

A reconstruction algorithm for electrical impedance tomography data collected on rectangular electrode arrays

A three-dimensional reconstruction algorithm in electrical impedance imaging is presented for determining the conductivity distribution beneath the surface of a medium, given surface voltage data measured on a rectangular array of electrodes. Such an electrode configuration may be desirable for using electrical impedence tomography to detect tumors in the human breast. The algorithm is based on linearizing the conductivity about a constant value. Here, we describe a simple implementation of the algorithm on a four-electrode--by-four-electrode array and the reconstructions obtained from numerical and experimental tank data. The results demonstrate significantly better spatial resolution in the plane of the electrodes than with respect to depth.     

Explaining the user experience of recommender systems

Research on recommender systems typically focuses on the accuracy of prediction algorithms. Because accuracy only partially constitutes the user experience of a recommender system, this paper proposes a framework that takes a user-centric approach to recommender system evaluation. The framework links objective system aspects to objective user behavior through a series of perceptual and evaluative constructs (called subjective system aspects and experience, respectively). Furthermore, it incorporates the influence of personal and situational characteristics on the user experience. This paper reviews how current literature maps to the framework and identifies several gaps in existing work. Consequently, the framework is validated with four field trials and two controlled experiments and analyzed using Structural Equation Modeling. The results of these studies show that subjective system aspects and experience variables are invaluable in explaining why and how the user experience of recommender systems comes about. In all studies we observe that perceptions of recommendation quality and/or variety are important mediators in predicting the effects of objective system aspects on the three components of user experience: process (e.g. perceived effort, difficulty), system (e.g. perceived system effectiveness) and outcome (e.g. choice satisfaction). Furthermore, we find that these subjective aspects have strong and sometimes interesting behavioral correlates (e.g. reduced browsing indicates higher system effectiveness). They also show several tradeoffs between system aspects and personal and situational characteristics (e.g. the amount of preference feedback users provide is a tradeoff between perceived system usefulness and privacy concerns). These results, as well as the validated framework itself, provide a platform for future research on the user-centric evaluation of recommender systems.     

Introducing the Internet to the over-60s: Developing an email system for older novice computer users

Contemporary technology offers many benefits to older people, but these are often rendered inaccessible through poor software design. As the Internet increasingly becomes a source of information and services it is vital to ensure that older people can access these resources. As part of project funded by the UK government, a multi-disciplinary team set out to develop usable software that would help to introduce older people to the Internet. The first step was to develop an email system for older people with no experience of Internet use. The project was intended to show that it is possible to design usable technology for this group and to explore some of the issues involved in doing so. Design and technical challenges necessitated various tradeoffs. The system produced demonstrated the success of the design decisions: it was significantly easier to use than, and preferred to, a commercial equivalent by a group of older people with no experience of Internet use.     

‘Best’ for whom?: the tension between ‘best practice’ ERP packages and diverse epistemic cultures in a university context

The idea that so-called ‘best’ business practices can be transferred to organizations when they purchase enterprise resource planning (ERP) software packages is a major selling point of these packages. Yet recent research has illustrated a gap between the espoused theory of a best practice solution and the theory-in-use experienced by those who install software with such a design. As researchers begin to examine the difficult process by which organizations recast the best practices model handed down to them by consultancies and software vendors in an effort to make the software ‘work for them’ in practice, it is equally important that we begin to understand the reasons that such a gap exists. To this end, we analyze the strategic partnership between a multinational software vendor and a university who together designed a ‘best practice’ ERP package for the higher education industry. Through the theoretical lens of ‘epistemic cultures’ we argue that in organizational contexts made up of more than one epistemic culture, the use of a best practice model will be problematic because, by definition, the model mandates one epistemological position through the software design. This is counter to a university's loosely coupled organizational form.     

The competitive assessment laboratory: introducing engineering design via consumer product benchmarking

In today's quickly changing and increasingly competitive market place, it is imperative that manufacturers keep abreast of the technological advances and design innovations incorporated into competing product lines. The term competitive assessment (or benchmarking) has been coined by manufacturers to describe the process of ethically acquiring, inspecting, analyzing, instrumenting, and testing the product lines of other manufacturers. The Competitive Assessment Laboratory at Rowan University is funded by the National Science Foundation (NSF). In the laboratory, multidisciplinary teams of freshman engineering students from each of the four engineering departments perform each of the above tasks on a consumer product. The laboratory contains a series of consumer appliance test stations featuring PC-based data acquisition systems capable of measuring thermocouple and voltage/current signals. Each station is also equipped with mechanical measurement equipment and portable materials testing equipment. In addition to introducing students to the science and art of design, the Competitive Assessment Laboratory enables the faculty to assess the constantly evolving initial conditions under which the typical engineering student enters his or her course of study.     

Relationship between intracranial pressure and the development of vasospasm after aneurysmal subarachnoid hemorrhage

The relationship between intracranial pressure (ICP) and the development of vasospasm after subarachnoid hemorrhage caused by the rupture of an intracranial aneurysm was investigated. Eleven patients were divided into high (6 cases) and low (5 cases) ICP groups based on ICP data obtained during the perioperative period by continuous ICP monitoring. Transcranial Doppler ultrasonography was performed every 24 hours for 7 days and the severity, distribution, and duration of vasospasm were assessed. The high ICP group tended to have severe, prolonged, and diffuse vasospasm compared with the low ICP group. However, only duration of vasospasm was statistically different. The relationship between cerebral perfusion pressure (CPP) and the development of vasospasm was also examined. CPP had a less significant effect than ICP although similar tendencies for high ICP and low CPP were observed. High ICP worsens vasospasm and treatment for decreasing ICP with perioperative ICP monitoring has potential for avoiding the development of vasospasm.     

An iterative Newton-Raphson method to solve the inverse admittivity problem

By applying electrical currents to the exterior of a body using electrodes and measuring the voltages developed on these electrodes, it is possible to reconstruct the electrical properties inside the body. This technique is known as electrical impedance tomography. The problem is nonlinear and ill conditioned meaning that a large perturbation in the electrical properties far away from the electrodes produces a small voltage change on the boundary of the body. This paper describes an iterative reconstruction algorithm that yields approximate solutions of the inverse admittivity problem in two dimensions. By performing multiple iterations, errors in the conductivity and permittivity reconstructions that result from a linearized solution to the problem are decreased. A finite-element forward-solver, which predicts voltages on the boundary of the body given knowledge of the applied current on the boundary and the electrical properties within the body, is required at each step of the reconstruction algorithm. Reconstructions generated from numerical data are presented that demonstrate the capabilities of this algorithm.     

Electrical impedance tomography of complex conductivitydistributions with noncircular boundary

Electrical impedance tomography (EIT) uses low-frequency current and voltage measurements made on the boundary of a body to compute the conductivity distribution within the body. Since the permittivity distribution inside the body also contributes significantly to the measured voltages, the present reconstruction algorithm images complex conductivity distributions. A finite element model (FEM) is used to solve the forward problem, using a 6017-node mesh for a piecewise-linear potential distribution. The finite element solution using this mesh is compared with the analytical solution for a homogeneous field and a maximum error of 0.05% is observed in the voltage distribution. The boundary element method (BEM) is also used to generate the voltage data for inhomogeneous conductivity distributions inside regions with noncircular boundaries. An iterative reconstruction algorithm is described for approximating both the conductivity and permittivity distributions from this data. The results for an off-centered inhomogeneity showed a 35% improvement in contrast from that seen with only one iteration, for both the conductivity and the permittivity values. It is also shown that a significant improvement in images results from accurately modeling a noncircular boundary. Both static and difference images are distorted by assuming a circular boundary and the amount of distortion increases significantly as the boundary shape becomes more elliptical. For a homogeneous field in an elliptical body with axis ratio of 0.73, an image reconstructed assuming the boundary to be circular has an artifact at the center of the image with an error of 20%. This error increased to 37% when the axis ratio was 0.64. A reconstruction algorithm which used a mesh with the same axis ratio as the elliptical boundary reduced the error in the conductivity values to within 0.5% of the actual values     

Velocity distribution in rectangular packed beds and non-ferrous blast furnaces

A theoretical equation for predicting velocity profiles in beds of rectangular geometry packed with equal-sized particles is presented. Use of this equation to predict velocity profiles requires the measurement of only one experimental variable. Predicted and measured velocity profiles in square and rectangular packed beds using a thermistor probe were in good agreement (±5 and ±10 pct respectively). For packings containing a range of sizes it was found that the velocity was greater at the wall and at the center of the bed than it was in the intermediate regions. This behavior, which has not been previously reported, is attributed to porosity variations. Results obtained from a slice model of a copper blast furnace indicate that in these furnaces there are two separate regions of flow. One of these has two components of velocity and the other has only one. In the single component flow region the velocity may be predicted by the theoretical equation presented. The implications of the results of this investigation to nonferrous blast furnaces are also discussed.