Youngseok Cho

Touch key design for target selection on a mobile phone

Mobile phones with a touch screen replacing traditional keypads have been introduced to the market. Few studies, however, have been conducted on the touch interface design for a mobile phone. This study investigated the effects of touch key sizes and locations on the one-handed thumb input that is popular in mobile phone interactions. Three different touch key sizes (i.e. square shape with 4mm, 7mm, and 10mm wide) and twenty five locations were examined in an experiment. The results provided two groups of touch key locations (an appropriate and an inappropriate region) with respect to three usability measures including success rate, number of errors, and pressing convenience. In addition, a hits distributions based algorithm was applied to target selection tasks, which statistically improved the performance. The results of this study could be used to design touch keys so as to enhance the usability of mobile phones with a touch screen.

Development of a Workload Assessment Model for Overhead Crane Operation

The operating tasks of overhead crane have caused undue stress to the operators from physical, mental, and environmental workload. Existing workload assessment models for musculoskeletal disorders such as OWAS, RULA, and QEC have limited applicability to the crane operating tasks because they focus mainly on physical factors and do not consider the relative importance of each factor. The present study was to develop a workload assessment model customized to overhead crane operation, following a systematic process: (1) analyzing task characteristics, (2) selecting workload factors, (3) developing assessment methods, (4) establishing action levels, and (5) computerizing the assessment model. Based on literature review, worksite survey, and focus group interview, 4 physical factors (awkward posture, static posture, repetitive motion, and excessive force), 6 mental factors (visual demand, auditory demand, task complexity and difficulty, time urgency, work schedule related stress, and safety related stress), and 4 environmental factors (noise, vibration, dust, and temperature) were selected and their rating scales and relative weights were determined. Then, based on the workload assessment results of 8 overhead cranes operated at different workplaces, the action levels of each factor category were established. Finally, the crane operation assessment model was computerized for effective analysis and report preparation. The present approach is applicable to develop a customized workload assessment model for an operating task under consideration.

Usability of adaptable and adaptive menus

This study investigates the usability of different adaptable and adaptive menu interfaces in a desktop environment. A controlled experiment was conducted to compare two different adaptive menus and one adaptable menu with a traditional menu. The two adaptive menus include an adaptive split menu that moves frequently used menu items to the top, and an adaptive highlight menu that automatically boldfaces frequently used menu items. Target selection times and the number of errors were recorded while the participants were performing menu selection tasks. Subjective satisfaction including perceived recognizability, perceived efficiency, and overall preference were also measured. The results showed that the adaptable menu outperformed the other menus in terms of both the performance and the satisfaction. The adaptive split menu was not as efficient as its theoretical prototype, especially when the selection frequency changed. The adaptive highlight menu, newly proposed in this study, was not significantly better than the traditional menu in terms of the selection time. However, it was preferred by the users since it helped them select frequently used items and was much less sensitive to the variations of selection frequency.

Developing User Interface Metaphors for Driver Information Systems

ABSTRACT This study proposed a practical metaphor development process that consisted of three steps: 1) identifying major functions, 2) developing metaphor candidates, and 3) evaluating appropriateness of the candidates. In the first step, a total of 27 functions might be implemented in a driver information system (DIS) in the near future. Then, three metaphor candidates were selected from existing metaphors, which were reported to be more practical than others by previous studies. Finally, the candidates were evaluated on their appropriateness for driver information systems by using a quick and simple survey. As a result, two metaphors (a PC and a secretary) were identified as the most appropriate ones. The two metaphors can be used to design a variety of interfaces and interactions for driver information systems. In addition, the development process proposed in this study could be applied to developing metaphors for emerging devices with a variety of functions (e.g. PMPs, MP3s, and electronic dictionaries) as well as driver information systems. Keyword: Driver information system (DIS), Metaphor, Menu naming & grouping, Mental model

Developing character input methods for driver information systems

This study proposes a framework for developing an input method to enter characters into a driver information system (DIS). The framework consists of two phases. The first phase is a conceptual design phase that helps to create and design conceptual input methods and to conduct formative evaluation. The second phase is a detail design phase that helps to design detailed interfaces and interaction, and to select the most usable character input method. A case study is conducted to verify the effectiveness of the developed methodology and to find appropriate input methods for knob control. As a result, character input methods appropriate for knob control were developed, which were proved to work more effectively than an existing method.