Participatory ergonomics in design processes: the role of boundary objects

The aim of this paper is to introduce the concept of boundary objects in order to better understand the role of objects in participatory ergonomics (PE) design processes. The research question is: What characterizes boundary objects in PE processes? Based on two case studies, we identify eight characteristics of boundary objects and their use, which make them particularly useful in PE design processes. These characteristics go beyond the object itself and extend into the context of their use. We argue that the selection of boundary objects in PE processes is of great importance, since different objects enable workers’ participation and collaborative design in different ways. The framework developed may serve to provide criteria to guide practitioners and intervention researchers in the selection of objects to facilitate a PE process. The paper concludes with a list of recommendations for ergonomic practitioners that are based on the framework.     

Safe mobility for elderly drivers—Considerations based on expert and self-assessment

To further understand the needs of the growing population of elderly drivers and create solutions for safe mobility it is important to understand the driving scenarios and aspects in day to day traffic that may be of challenge for this group. More so, individual differences in how drivers perceive their own driving ability may have an effect on how individuals limit their mobility and/or increase their exposure to risk situations, with a potential negative effect on safety.     

Methods and Procedures for Computer Based Handling of Components Reliability Data at FTL (The Swedish Military Electronics Laboratory)

In order to turn reliability prediction into a readily available tool, a system for computerized handling of failure rates was developed at FTL. This system, which is named RPP-1 (Reliability Program One) is presently covering data of electronic and electromechanical components. From a given list of components and data on stresses and working conditions, the failure rates are automatically searched, processed, and pooled in an assessment for an equipment. To make this possible, a number of decisions and judgements had to be taken regarding codes, formulas, models, bank structure, application factors, etc. This paper gives a summary of the FTL solutions for those basic questions. The system?actually a system of subprograms?has been developed at the Swedish Military Electronics Laboratory. The project was headed by the the author of this paper.     

Double auction-inspired meta-scheduling of parallel applications on global grids

Meta-schedulers map jobs to computational resources that are part of a Grid, such as clusters, that in turn have their own local job schedulers. Existing Grid meta-schedulers either target system-centric metrics, such as utilisation and throughput, or prioritise jobs based on utility metrics provided by the users. The system-centric approach gives less importance to users’ individual utility, while the user-centric approach may have adverse effects such as poor system performance and unfair treatment of users. Therefore, this paper proposes a novel meta-scheduler, based on the well-known double auction mechanism that aims to satisfy users’ service requirements as well as ensuring balanced utilisation of resources across a Grid. We have designed valuation metrics that commodify both the complex resource requirements of users and the capabilities of available computational resources. Through simulation using real traces, we compare our scheduling mechanism with other common mechanisms widely used by both existing market-based and traditional meta-schedulers. The results show that our meta-scheduling mechanism not only satisfies up to 15% more user requirements than others, but also improves system utilisation through load balancing.     

Learners as Knowledge Workers—Some Implications*

Traditionally, behavioristic models have been used for the design of interactive learning environments. In contrast, this paper proposes a pedagogical model based on social constructionism and phenomenology which we believe is more adequate when, for instance, information seeking and WWW become natural components in the learning situation. In this model, learners are seen as persons who continuously alter their conceptions and ideas by working with data, information, and knowledge, i.e. learners as knowledge workers. The most important point in viewing learners as knowledge workers is exactly that the learners change their understanding by working with the information, and that they do that with the help of cognitive tools. I see it as a necessity that the learning environment consists of tools that support them in their learning processes: tools for constructing, processing and observing information, data, and knowledge. Equally important in this new kind of learning situation are tools to establish and maintain focus, manage information overload, to bridge distances in the learning situation, and to communicate.     

A novel integrated optics wavelength filter in InGaAsP-InP

An InGaAsP-InP integrated optics wavelength selective device is proposed and demonstrated. It utilizes coupling between epitaxial layers with different refractive indices and thicknesses. The device is suitable for integration to form, e.g., a monolithic receiver for wavelength division multiplexed optical communication systems. Design considerations are given. The filter bandwidth and center wavelength can be freely chosen, and bandwidths as narrow as 1.5 nm at 1.3 or 1.55 μm center wavelength are shown feasible. Electrical tuning is possible. Experimental filters show that devices can he fabricated with performance in good agreement with theory, The 22-nm -3-dB bandwidth at 1.12-μm center wavelength presently demonstrated is limited by the measurement system.     

Very low-threshold 1.53?m DFB lasers by VPE transport

DFB lasers with CW threshold currents as low as 8 mA at room temperature have been fabricated using the VPE transport process. The low threshold currents are attributed to narrow active stripes and to the high coupling strength of the grating. Single-mode lasing at 1.53?m up to I = 8Ith and during high-speed direct modulation has been confirmed.     

A Smooth Dissipative Region Model

A Barenblatt model of the dissipative region at the edge of a mode I crack under small scale yielding is established, so that stress gradient and displacement gradient continuity prevail along the symmetry plane. The resulting model thus connects smoothly to adjacent material and it displays exceptionally smooth opening.     

How fast can a crack go?

The assumption of a material specific relation between the energy dissipation at the edge of a crack propagating under small scale yielding conditions leads to upper limits of the crack velocity: the Rayleigh wave velocity for modes I and II, and theS wave velocity for mode III. If a mode II crack can pass the “forbidden” subsonic super-Rayleigh region, then the upper limit would be theP wave velocity. Experiments invariably show lower maximum speeds, typically less than 60% of theS wave velocity, but they also frequently show accelerations to a constant velocity, depending on the acceleration history, and increasing surface roughness, even during the constant velocity phase. Other experiments show that the energy dissipation at the crack edge usually is several times larger at very high than at very low velocities. These results indicate a considerable growth of the process region, so much that the intrinsic length parameter which determines its height at very low crack speeds becomes insignificant, and then the rationale for a material specific relation between energy dissipation and velocity disappears. This disappearance can contribute to the explanation of the experimental results. Department of Mathematical Physics, University College Dublin, Belfield, Dublin, Ireland. Published in Fizyko-Khimichna Mekhanika Materialiv, Vol. 32, No. 1, pp. 91–98, January–February, 1996.