As cell phones have expanded their functionality with enhanced mobile technology, use of cell phones has become complex. Although usability of cell phones has been improved by featuring hierarchical menu systems, designing comprehensible navigation in the menu hierarchy is still a major challenge to cell phone user interface (UI) developers as more diverse users are adopting cell phones. To develop an easy-to-use cell phone UI, an effective usability evaluation method (UE) is essential. While various usability evaluation methods (UEM) have been developed, laboratory-based usability testing produces high-quality usability data from actual users. Yet, the effectiveness of such testing can vary dramatically depending on what data is collected and how the data are analyzed. To provide a practical guidance for the effective laboratory testing, we developed a systematic evaluation methodology for cell phone user interfaces (SEM-CPU). SEM-CPU is specifically designed to integrate five empirical methods (scenario-based task performance, questionnaires, posttask interview, user observation, and retrospective think aloud) into a laboratory-based test in order to evaluate cell phone UIs. By following SEM-CPU, usability engineers should be able to (1) conduct laboratory-based testing with multiple empirical methods in an efficient way, (2) collect diverse but useful data to measure necessary usability attributes, (3) identify determinants of usability problems, and (4) integrate all usability data to generate proper solutions for the problems. (Y.S. Lee).Detailed descriptions of SEM-CPU are presented along with a case study where SEM-CPU was applied to a comparative cell phone usability test. q
Seven healthy young male students participated in this study. Each subject sat on a chair in an anteroom at 25 degrees C for 30 min and then entered a climatic chamber, controlled at 40 degrees C and R.H. 50%, and sat on a chair for 90 min. Cooling of frontal portion including the region around the eyes (FC), occipital portion (OC), and temporal portion (TC) began after 50 min of entering. An experiment without head cooling (NC) was also made for the control measurement. Thermal comfort and thermal sensation were improved by head cooling, but response was the same regardless of portion cooled. Although rectal temperature, mean skin temperature and heart rate showed no significant effect due to head cooling, forearm skin blood flow (FBF), sweat rate (SR), and body weight loss (delta Wt) had a tendency to be depressed. FBF in FC and TC decreased during head cooling, but that in OC and NC did not change significantly, while SR in FC was depressed. delta Wt showed total sweating to decrease by FC and TC, and FC to have greater inhibitory effect on sweating than OC. Thermal strain was evaluated by the modified Craig Index (I(s)). I(s) in FC decreased significantly more than in NC. Cooling of other portions of the head had no significant effect on I(s). Cooling of the frontal portion of the head may thus be concluded to have the most effect on thermoregulatory response in a hot environment.
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