Design Assessment of Two-Wheeled Luggage Based on Mechanical Models and a Usability Test

The purpose of this study is to ergonomically assess two-wheeled luggage design based on mechanical models and a usability test. Three mechanical models were developed for the pulling force estimation and important luggage design factor finding. Three pulling conditions with three motion stages were considered in the model. In addition, a set of pre-questionnaires and a set of post-questionnaires were prepared for the investigation of users’ preferences for each design factor. From the mechanical models, the minimum pulling force was found at the tilted angle of 65.56° in static staus, at the tilted angle of 30° in the initial phase, and at the tilted angle of 65.56° in the sustained phase. Based on the optimal tilted angle, several pole lengths were suggested (41.5” for 5%ile female, 45.5” for 5%ile male and 50%ile female groups, 49.5” for 50%ile male, 95%ile female groups, and 52.5” for 95%ile male group). In addition, some important design factors contributory to the minimum pulling force were found through the mechanical models. According to the results of mechanical models, tilted angles of luggage(), the distance between center of mass and the bottom of luggage (b), and weight of luggage (W) significantly affected the pulling force. Two luggage prototypes were developed by considering the important design factors resulted from the mechanical models and a usability test was conducted. For the usability test, two load weights (33 lbs and 50 lbs), six pole lengths (38.5”, 41.5”, 44.5”, 45.5”, 49.5”, and 52.5”), four subject groups (5%ile female, 50%ile female, 50%ile male, and 95%ile male groups), and two luggage size (22”×14”×10” and 30”×21”×11.5”) were considered in experimental design. Subjects answered pre- and post-questionnaires as soon as they conducted the experiment. Test results demonstrated that most upper body parts were affected by load weights, pole length, and subjects’ knuckle heights. In addition, pole lengths between 38.5” and 49.5” were selected from all subject groups. A pole should be adjustable within the range from 38.5” to 49.5” although the mechanical models suggested the pole lengths between 38.5” and 52.5”. Tilted angle should be maintained from 30º to 50º in this range. This result indicated that there is a gap between the theoretical and practical results. In conclusion, load weights, pole lengths, and subjects’ knuckle heights should primarily be considered when luggage is designed. However, additional studies need to get deeper understanding of the gap between mechanical models and usability. In addition, more systematical survey questionnaires should be developed to provide any possible solutions to reduce the gap

The Light Radion Window

Inspired by the Contino-Pomarol-Rattazzi mechanism we explore scenarios with a very light (100 keV to 10 GeV) radion which could be associated with the suppression of the electroweak contribution to vacuum energy. We construct explicit, realistic models that realize this mechanism and explore the phenomenological constraints on this class of models. Compared with axion-like particles in this mass range, the bounds from SN 1987a and from cosmology can be much weaker, depending on the the mass of the radion and its coupling to other particles. With couplings suppressed by a scale lower than 100 TeV much of the mass window from 100 keV to 10 GeV is still open.Comment: 30 pages, 12 figures, published version, software for figure uploade