Taebeum Ryu

Determination of Critical Design Variables Based on the Characteristics of Product Image/Impression: Case Study of Office Chair Design

Based on the assumption that the characteristics of product image/impression can be estimated by consumer preference rating, this study performed an image/impression evaluation of various office chair designs. The purpose of this study was to specify the design variables significantly affecting customer preference of the product. Sixty subjects evaluated fifty different office chair designs on thirteen aspects of product image/impression categories using the modified magnitude estimation method. At the same time, forty-eight design variables were selected and analyzed from the same set of office chairs. Multiple linear regression modeling technique was used to model the relationship between the image/impression scores and the design variables. The range of customer response on image/impression categories, the sensitivity of the customer response, and the degree of customer satisfaction on the products were further analyzed using a 3-dimensional portfolio plotting. The result showed that the product image/impression were closely related to the degree of customer satisfaction on the product. The result also showed that the design of office chairs can be improved by focusing on the design variables specified from the 3-D portfolio plot.

Relationships of Musculoskeletal Disorder Symptoms and Perceived Workload among Hospital Workers

Objective: This study aims to survey the prevalence of musculoskeletal disorders(MSD) among Korean hospital workers and to analyze the relationship of MSD symptoms and workload perceived by workers. Background: Despite of high exposure to the MSD risk factors and high MSD symptom prevalence among health care workers, there were not enough studies of MSD prevalence among the hospital workers. Method: This study designed a survey based on Nordic questionnaire to obtain MSD symptoms and the degree of four perceived workloads: work repetition, urgency, physical exertion and satisfaction. In this survey, 1,846 workers in a hospital participated. The prevalence of MSD was analyzed for each body part, and MSD cases, which were predetermined in this study, were identified. The relationship between the MSD cases and each perceived workload was analyzed using chi-square test. Results: The pain in the shoulder was the most prevalent among the workers as 52%, and the low back(37%) and leg discomfort(36%) followed. The MSD cases, in which degree of pain was more than severe, were also the most prevalent in the shoulder(13%). Female workers had higher rate of MSD cases than the males. Among the four workload variables, the physical exertion was the statistically related to MSD cases for all the body parts. In addition, the others also had significant relation to MSD cases except one or two body parts. Conclusion: This study found that Korean hospital workers had MSD symptoms mainly in the shoulder, low back and legs in order, and the perceived workload surveyed in this study was highly correlated with MSD symptoms. Application: This study provides another evidence that subjective physical exertion perceived by workers is an important factor to explain MSD cases as same as the objective one.

Performance Analysis of Text Entry with Preferred One Hand using Smart Phone Touch-keyboard

Is performance in smartphone text entry better when using the preferred hand rather than the non-preferred hand? Among right-handed people, is the performance of users who prefer using their left hand in smartphone text entry worse than that of users who prefer using their right hand? The present study addresses these questions. Thirty young male undergraduate students were instructed to type a text message template using a thumb-based QWERTY smartphone with both hands, with only their right hand, and with only their left hand. The completion time and occurrence of errors were measured. All participants were right handed. However, when only one hand is available half of them preferred to use their right hand if they had to enter a text on the smartphone, whereas the other half preferred to use their left hand. In entering a text with only one hand, about 90% of the 15 righthand-preferred participants, and about 70% of the 15 lefthand-preferred participants performed better using their preferred hand than using their nonpreferred hand. However, the performance of the participants who performed better using their left hand was not worse than those who performed better using their right hand in smartphone text entry.

Survey of Musculoskeletal Disorders in Korean Dentists

Dentists are known to be highly exposed to the musculoskeletal disorders (MSD). The present study investigated the prevalence of MSD among Korean dentists and association between their MSD and physical workload. In addition, work-related causes of high physical workload were identified and needs of dentists were collected for improvement of dental instrument and environment. Four types of questionnaires including the Nordic questionnaire were used to investigate body troubles, physical workload, causes of physical workload, and improvement priority of dental components. A total of 104 dentists in Seoul were participated in the survey. Neck trouble (82%) was the most prevalent in the participated dentists and shoulder (68%) and low back trouble (56%) followed, while low back trouble was reported to be most common in previous western studies. The body troubles were related to the physical workload of the corresponding body parts, although they were not associated with personal characteristics. Most dentists selected `to keep direct view inside patient`s mouth` and `no support of the hand with dental instruments` as causes of awkward and strenuous work postures. They wanted design improvement for some components in their operating room such as operating light and arrangement of workplace.

Development of Satisfaction Models for Passenger Car Interior Materials Considering Statistical and Engineering Aspects of Design Variables

As the functionality of a passenger car has reached at a satisfactory level, customer needs for aesthetic aspects of a design such as shape and material become increased. The present study developed satisfaction models for passenger car interior materials by applying methods of variable screening and recoding. Six interior parts of a passenger car were selected including crash pad, steering wheel, transmission gearshift knob, audio panel, and wooden/metal grain. Eight to fifteen material design variables were defined for the six interior parts. A satisfaction survey was conducted to 30 vehicles with 30 participants (mean (SD) of 28.7 (6.6) in age) by using a modified magnitude estimation scale. Methods of variable screening/recoding were proposed to develop models that are stable and of statistical/practical significance. By applying the variable screening/recoding methods to the surveyed satisfaction data, satisfaction models were developed for the six interior parts. Using the satisfaction models, material designs to improve customer satisfaction were prepared and their potential effects were estimated.

Effects of Visual Stimulus on Response Behavior of Control-on-Display Interface

Control-on-display interfaces enable a direct and intuitive manipulation by inducing control directly through the visual stimuli, thereby reducing information-processing stages and improving feed-forward property. The visual information displayed on such devices act not only as visual stimuli but also as controllers. This study investigated the effect of visual stimulus on users’ response behavior while using touch screen. Three characteristics of visual stimulus were investigated: (a) shape of visual stimulus requesting simple tap reaction, (b) contrast between figure and background, and (c) existence of precue on upcoming event. The effects of the selected factors were tested using the response time and the response accuracy measured by 2D deviation vectors. A full factorial experimental design, followed by a multivariate analysis of variance and pairwise comparisons showed that the shift of the center of area from the circumcenter of the stimuli affects the location where fingertip touched, the different background contrast affects both the time and accuracy, and it is confirmed that precue speeds up the response times and improves accuracy in control-on-display interaction.

Conditions of applications, situations and functions applicable to gesture interface

Although there were many studies related to developing new gesture-based devices and gesture interfaces, it was little known which applications, situations and functions are applicable to gesture interface. This study developed a hierarchy of conditions of applications (devices), situations and functions which are applicable to gesture interface. This study searched about 120 papers relevant to designing and applying gesture interfaces and vocabulary to find the gesture applicable conditions of applications, situations and functions. The conditions which were extracted from 16 closely-related papers were rearranged, and a hierarchy of them was developed to evaluate the applicability of applications, situations and functions to gesture interface. This study summarized 10, 10 and 6 conditions of applications, situations and functions, respectively. In addition, the gesture applicable condition hierarchy of applications, situation and functions were developed based on the semantic similarity, ordering and serial or parallel relationship among them. This study collected gesture applicable conditions of application, situation and functions, and a hierarchy of them was developed to evaluate the applicability of the gesture interface.

Development of a Hierarchical Estimation Method for Anthropometric Variables

Most regression models of anthropometric variables use stature and/or weight as regressors; however, these ‘flat’ regression models result in large errors for anthropometric variables having low correlations with the regressors. For better accuracy in estimating anthropometric variables, this study proposed a method to estimate anthropometric variables in a hierarchical manner based on the geometric and statistical relationships among the variables. By applying the proposed approach to 60 anthropometric variables selected for the design of an occupant package layout in a passenger car, hierarchical estimation structures were constructed and then based on the estimation structures hierarchical regression models were developed with the 1988 US Army anthropometric survey data. The hierarchical regression models were compared with the corresponding flat regression models in terms of adjusted R2 and SE, resulting in on average a 55% increase in adjusted R2 and a 31% decrease in SE when compared to the corresponding flat models.

Conditions of Applications, Situations and Functions Applicable to Gesture Interface

Objective: This study developed a hierarchy of conditions of applications(devices), situations and functions which are applicable to gesture interface. Background: Gesture interface is one of the promising interfaces for our natural and intuitive interaction with intelligent machines and environments. Although there were many studies related to developing new gesture-based devices and gesture interfaces, it was little known which applications, situations and functions are applicable to gesture interface. Method: This study searched about 120 papers relevant to designing and applying gesture interfaces and vocabulary to find the gesture applicable conditions of applications, situations and functions. The conditions which were extracted from 16 closely-related papers were rearranged, and a hierarchy of them was developed to evaluate the applicability of applications, situations and functions to gesture interface. Results: This study summarized 10, 10 and 6 conditions of applications, situations and functions, respectively. In addition, the gesture applicable condition hierarchy of applications, situation and functions were developed based on the semantic similarity, ordering and serial or parallel relationship among them. Conclusion: This study collected gesture applicable conditions of application, situation and functions, and a hierarchy of them was developed to evaluate the applicability of gesture interface. Application: The gesture applicable conditions and hierarchy can be used in developing a framework and detailed criteria to evaluate applicability of applications situations and functions. Moreover, it can enable for designers of gesture interface and vocabulary to determine applications, situations and functions which are applicable to gesture interface.

The Effect of a Wedged Rocker Sole on Ankle Joints during Gait

Wedged soles and rocker soles are widespread shoe designs used to prevent the disorders and reduce the pain of the lower extremity caused by arthritis or diabetic feet. In this study, the effect of a shoe with a laterally wedged sole and a rocker sole simultaneously was analyzed on the kinematics and kinetics of the ankle joint during normal walking. Eight male participants without a history of lower extremity disorders were recruited. Each participant performed twenty walking cycles for each of three walking conditions: bare foot, wearing normal shoes and wearing shoes with laterally wedged rocker soles. The differences between the three walking conditions were statistically investigated including spatio-temporal variables, angular displacements, joint moments and ground reaction forces. The results showed that the laterally wedged rocker sole decreased the sagittal variation of angular displacements as well as the frontal/sagittal average moment on the ankle joints compared to the flat sole. In addition, the rate of angular displacements and loading decreased during the heel contact phase.