Usability evaluation of systems for mobile computers and devices is an emerging area of research. This paper presents and evaluates six techniques for evaluating the usability of mobile computer systems in laboratory settings. The purpose of these techniques is to facilitate systematic data collection in a controlled environment and support the identification of usability problems that are experienced in mobile use. The proposed techniques involve various aspects of physical motion combined with either needs for navigation in physical space or division of attention. The six techniques are evaluated through two usability experiments where walking in a pedestrian street was used as a reference. Each of the proposed techniques had some similarities to testing in the pedestrian street, but none of them turned out to be completely comparable to that form of field-evaluation. Seating the test subjects at a table supported identification of significantly more usability problems than any of the other proposed techniques. However a large number of the additional problems identified using this technique were categorized as cosmetic. When increasing the amount of physical activity, the test subjects also experienced a significantly increased subjective workload. r
In conventional underlay tympanoplasty the graft is placed medial to the malleus handle. The present study evaluates the results of a modification of this technique, in which the graft is placed lateral to the malleus handle, which has been dissected from the drum remnants. 39 ears with predominantly large or anterior pars tensa perforations were operated upon in this manner. After a median observation time of 20 months one ear was found to have a small reperforation. All ears had normal tympanomeatal angles, but 12 ears showed a small degree of laterofixation of the graft from the malleus handle. Analysis of the hearing showed good hearing improvement and no adverse effects attributable to the dissection of the ossicular chain. It is concluded that the technique is a good alternative to conventional underlay myringoplasty in ears with perforations involving the area anterior to the malleus handle.
The effect of the H2-receptor blocking agent cimetidine on jejunal effluent was examined in eight short-bowel patients with high-output jejunostomies. Stool mass and faecal excretion of sodium and potassium were significantly reduced by intravenous injection of 400 mg cimetidine four times a day. The amount of calcium, magnesium, phosphate, zinc, and fat in jejunostomy effluent did not change significantly. Cimetidine may be considered an antidiarrhoeal drug in extensively small-bowel-resected patients with a jejunostomy and may reduce the need for parenteral saline supply in these patients.
Compares experimental (eg. prototyping) and analytical (eg.
specifying) approaches in systems design. Derives ′The Principle of
Limited Reduction′. Defines this as: “Relying on an analytical
mode of operation to reduce complexity introduces new sources of
uncertainty requiring experimental countermeasures; relying on an
experimental mode of operation to reduce complexity introduces new
sources of uncertainty requiring analytical countermeasures”.
Concludes that a mixed approach is best, but warns that this is as yet
(1992) hypothetical.
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