Gaze Path Stimulation in Retrospective Think-Aloud

For a long time, eye tracking has been thought of as a promising method for usability testing. During the last couple of years, eye tracking has finally started to live up to these expectations, at least in terms of its use in usability laboratories. We know that the user’s gaze path can reveal usability issues that would otherwise go unnoticed, but a common understanding of how best to make use of eye movement data has not been reached. Many usability practitioners seem to have intuitively started to use gaze path replays to stimulate recall for retrospective walk through of the usability test. We review the research on thinkaloud protocols in usability testing and the use of eye tracking in the context of usability evaluation. We also report our own experiment in which we compared the standard, concurrent think-aloud method with the gaze path stimulated retrospective think-aloud method. Our results suggest that the gaze path stimulated retrospective think-aloud method produces more verbal data, and that the data are more informative and of better quality as the drawbacks of concurrent think-aloud have been avoided

A simple model for the time evolution of the condensation sink in the atmosphere for intermediate Knudsen numbers

Transformation of the mass flux towards the particle from the kinetic regime to the continuum regime is often described by the Fuchs-Sutugin coefficient. Kinetic regime can be obtained as a limiting case when only one term of the expansion of the Fuchs-Sutugin coefficient at small 1/Kn is considered. Here we take the two first terms into account, and get a mass flux which agrees well with the full mass flux down to Kn similar to 0.5. This procedure allows an analytical solution of the condensation equation valid for the range of intermediate Knudsen numbers to be obtained. The expansion is further applied to analytically calculate the condensation sink. The formula for the condensation sink is tested against field observations. The relative contribution of different aerosol modes to the condensation sink is discussed. Furthermore, we present a simple model describing the coupled dynamics of the condensing vapour and the condensation sink. The model gives reasonable predictions of condensation sink dynamics during the periods of the aerosol modes' growth by condensation in the atmosphere.Peer reviewe

Aerosol formation and growth rates from chamber experiments using Kalman smoothing

Bayesian state estimation in the form of Kalman smoothing was applied to differential mobility analyser train (DMA-train) measurements of aerosol size distribution dynamics. Four experiments were analysed in order to estimate the aerosol size distribution, formation rate, and size-dependent growth rate, as functions of time. The first analysed case was a synthetic one, generated by a detailed aerosol dynamics model and the other three chamber experiments performed at the CERN CLOUD facility. The estimated formation and growth rates were compared with other methods used earlier for the CLOUD data and with the true values for the computer-generated synthetic experiment. The agreement in the growth rates was very good for all studied cases: estimations with an earlier method fell within the uncertainty limits of the Kalman smoother results. The formation rates also matched well, within roughly a factor of 2.5 in all cases, which can be considered very good considering the fact that they were estimated from data given by two different instruments, the other being the particle size magnifier (PSM), which is known to have large uncertainties close to its detection limit. The presented fixed interval Kalman smoother (FIKS) method has clear advantages compared with earlier methods that have been applied to this kind of data. First, FIKS can reconstruct the size distribution between possible size gaps in the measurement in such a way that it is consistent with aerosol size distribution dynamics theory, and second, the method gives rise to direct and reliable estimation of size distribution and process rate uncertainties if the uncertainties in the kernel functions and numerical models are known.Bayesian state estimation in the form of Kalman smoothing was applied to differential mobility analyser train (DMA-train) measurements of aerosol size distribution dynamics. Four experiments were analysed in order to estimate the aerosol size distribution, formation rate, and size-dependent growth rate, as functions of time. The first analysed case was a synthetic one, generated by a detailed aerosol dynamics model and the other three chamber experiments performed at the CERN CLOUD facility. The estimated formation and growth rates were compared with other methods used earlier for the CLOUD data and with the true values for the computer-generated synthetic experiment. The agreement in the growth rates was very good for all studied cases: estimations with an earlier method fell within the uncertainty limits of the Kalman smoother results. The formation rates also matched well, within roughly a factor of 2.5 in all cases, which can be considered very good considering the fact that they were estimated from data given by two different instruments, the other being the particle size magnifier (PSM), which is known to have large uncertainties close to its detection limit. The presented fixed interval Kalman smoother (FIKS) method has clear advantages compared with earlier methods that have been applied to this kind of data. First, FIKS can reconstruct the size distribution between possible size gaps in the measurement in such a way that it is consistent with aerosol size distribution dynamics theory, and second, the method gives rise to direct and reliable estimation of size distribution and process rate uncertainties if the un-certainties in the kernel functions and numerical models are known.Peer reviewe

The client's essential stakeholder collaboration activities at the front-end phase of a hospital construction project

Purpose: The research problem in this study is how a client (as a project owner) should organise early stakeholder involvement and integration in the front-end phase of a project. This study aims to create normative managerial statements as propositions from the client's perspective and to combine them into a set of activities enabling efficient organisation in the front-end phase of a hospital construction project. Design/methodology/approach: Action design research (ADR) was carried out in a large hospital construction project where the first author acted as an “involved researcher” and the other authors acted as “outside researchers”. Findings: The authors created seven normative managerial propositions that were verified by the case project stakeholders and developed a managerial framework describing the client's essential stakeholder involvement and integration activities in the front-end phase of a hospital construction project based on these propositions. The authors have also depicted the subphases of the front-end phase: value definition phase in the client permanent organisation, value proposition phase in the client Programme Management Office (PMO) and finally development phase in the alliance organisation ending on the final investment decision. Practical implications: The collaborative contract delivery model enables the early involvement and integration of stakeholders. It has been somewhat surprising to note the extent to which collaborative contracts change the client role in the project front-end. The results offer practical activities for how clients can manage front-end activities in collaborative contracts. Originality/value: The case project offered a platform to analyse how the collaborative contract delivery model changes the emphasis of activities in the front-end of a project. One of the key benefits of collaborative contracts is that development, design and delivery occur partially in parallel, thereby enabling contributions from production to be included in the design and development. The benefit of having a real-life case under study provides the possibility to triangulate and analyse rich data, however limited by the qualitative case method.Peer reviewe