Development of a human-friendly visual inspection method for painted vehicle bodies.

Visual inspections performed in the final stage of the vehicle manufacturing process are crucial for assuring the quality of painted vehicle bodies. However, lengthy visual inspections can cause fatigue and discomfort of the eyes, which may adversely affect inspection accuracy and efficiency. This study developed a new human-friendly visual inspection method for the detection of defects (e.g., scar and dent) on vehicle bodies, and compared its performance to a conventional inspection method in terms of critical fusion frequency (Hz, indirect measure of eye fatigue), defect detectability (%), and subjective satisfaction score (7-point Likert scale). The new method was devised to project bright-dark linear stripes onto the surface of the vehicle body and created emergent features (distorted stripes) where a defect existed. The critical fusion frequency of the new method decreased slightly (3.7%) after a 30-minute visual inspection task, whereas that of the conventional method dropped substantially (11.0%), which implied more severe eye fatigue. Additionally, the new method had significantly higher defect detectability (92.1%) and satisfaction score (5.8 points) than those (73.4% and 3.5 points) of the conventional method.

Analysis of natural finger-press motions for design of trackball buttons.

This study analysed natural press motions of the index, middle and ring fingers for ergonomic design of the positions and surface angles of the left, middle and right trackball buttons. Finger motions of 26 male participants for naturally pressing the trackball buttons were recorded after the participants adjusted the trackball buttons to their preferred locations for comfortable pressing. The natural positions of the finger pulps formed a symmetrically rainbow-shaped reach zone for the fingers. The natural press angles of the fingers' motion trajectories to the vertical reference line ranged from 14.2° to 20.5°, suggesting an 18-degree surface from the horizontal line for the trackball buttons. Regression formulas (adjusted R2 = 0.90 ± 0.07 and mean squared error = 8.55 ± 7.52 mm) were established to estimate the natural positions of finger pulps from hand segment lengths and joint angles for a population having different hand sizes from this study. Relevance to industry.

Glasses-type wearable computer displays: usability considerations examined with a 3D glasses case study.

This study presents usability considerations and solutions for the design of glasses-type wearable computer displays and examines their effectiveness in a case study. Design countermeasures were investigated by a four-step design process: (1) preliminary design analysis; (2) design idea generation; (3) final design selection; and (4) virtual fitting trial. Three design interventions were devised from the design process: (1) weight balance to reduce pressure concentrated on the nose, (2) compliant temples to accommodate diverse head sizes and (3) a hanger mechanism to help spectacle users hang their wearable display on their eye glasses. To investigate their effectiveness, in the case study, the novel 3D glasses adopting the three interventions were compared with two existing 3D glasses in terms of neck muscle fatigue and subjective discomfort rating. While neck muscle fatigue was not significantly different among the three glasses (p = 0.467), the novel glasses had significantly smaller discomfort ratings (p = 0.009). Relevance to Industry: A four-step design process identified usability considerations and solutions for the design of glasses-type wearable computer displays. A novel 3D glasses was proposed through the process and its effectiveness was validated. The results identify design considerations and opportunities relevant to the emerging wearable display industry.

Investigation of index finger triggering force using a cadaver experiment: Effects of trigger grip span, contact location, and internal tendon force.

A cadaver study was conducted to investigate the effects of triggering conditions (trigger grip span, contact location, and internal tendon force) on index finger triggering force and the force efficiency of involved tendons. Eight right human cadaveric hands were employed, and a motion simulator was built to secure and control the specimens. Index finger triggering forces were investigated as a function of different internal tendon forces (flexor digitorum profundus + flexor digitorum superficialis = 40, 70, and 100 N), trigger grip spans (40, 50, and 60 mm), and contact locations between the index finger and a trigger. Triggering forces significantly increased when internal tendon forces increased from 40 to 100 N. Also, trigger grip spans and contact locations had significant effects on triggering forces; maximum triggering forces were found at a 50 mm span and the most proximal contact location. The results revealed that only 10-30% of internal tendon forces were converted to their external triggering forces.

Development of a press and drag method for hyperlink selection on smartphones.

The present study developed a novel touch method for hyperlink selection on smartphones consisting of two sequential finger interactions: press and drag motions. The novel method requires a user to press a target hyperlink, and if a touch error occurs he/she can immediately correct the touch error by dragging the finger without releasing it in the middle. The method was compared with two existing methods in terms of completion time, error rate, and subjective rating. Forty college students participated in the experiments with different hyperlink sizes (4-pt, 6-pt, 8-pt, and 10-pt) on a touch-screen device. When hyperlink size was small (4-pt and 6-pt), the novel method (time: 826 msec; error: 0.6%) demonstrated better completion time and error rate than the current method (time: 1194 msec; error: 22%). In addition, the novel method (1.15, slightly satisfied, in 7-pt bipolar scale) had significantly higher satisfaction scores than the two existing methods (0.06, neutral).

Development of a usability evaluation method using natural product-use motion.

The present study developed and tested a new usability evaluation method which considers natural product-use motions. The proposed method measures both natural product-use motions (NMs) and actual product-use motions (AMs) for a product using an optical motion capture system and examines the usability of the product based on motion similarity (MS; %) between NMs and AMs. The proposed method was applied to a usability test of four vacuum cleaners (A, B, C, and D) with 15 participants and their MSs were compared with EMG measurements and subjective discomfort ratings. Cleaners A (44.6%) and C (44.2%) showed higher MSs than cleaners B (42.9%) and D (41.7%); the MSs mostly corresponded to the EMG measurements, which could indicate that AMs deviated from NMs may increase muscular efforts. However, the MSs were slightly different from the corresponding discomfort ratings. The proposed method demonstrated its usefulness in usability testing, but further research is needed with various products to generalize its effectiveness.

Effects of button position on a soft keyboard: Muscle activity, touch time, and discomfort in two-thumb text entry.

Intensive use of the thumbs for text entry on smartphones may contribute to discomfort, pain, or musculoskeletal disorders. This study investigated the effect of twenty-five button positions (5 rows × 5 columns) on a soft keyboard for two-thumb entry. Two experiments measured muscle activity, touch time, and discomfort as a function of the button positions. In Phase I, the muscle activities of two intrinsic (abductor pollicis brevis and first dorsal interossei) and two extrinsic (abductor pollicis longus and extensor digitorum communis) muscles associated with thumb motions were observed for ten college students (age: 24.2). In Phase II, touch time and discomfort were measured for 40 college students (age: 23.6). The results demonstrated that the %MVCs of the intrinsic muscles significantly increased when the thumbs flexed and abducted. Also, the button positions near the rest positions of the thumbs resulted in significantly shorter touch times (0.66 s) and lower discomfort ratings (0.70 pt) than their peripheral buttons (0.76 s; 2.29 pt).

Classification of a Driver's cognitive workload levels using artificial neural network on ECG signals.

An artificial neural network (ANN) model was developed in the present study to classify the level of a driver's cognitive workload based on electrocardiography (ECG). ECG signals were measured on 15 male participants while they performed a simulated driving task as a primary task with/without an N-back task as a secondary task. Three time-domain ECG measures (mean inter-beat interval (IBI), standard deviation of IBIs, and root mean squared difference of adjacent IBIs) and three frequencydomain ECG measures (power in low frequency, power in high frequency, and ratio of power in low and high frequencies) were calculated. To compensate for individual differences in heart response during the driving tasks, a three-step data processing procedure was performed to ECG signals of each participant: (1) selection of two most sensitive ECG measures, (2) definition of three (low, medium, and high) cognitive workload levels, and (3) normalization of the selected ECG measures. An ANN model was constructed using a feed-forward network and scaled conjugate gradient as a back-propagation learning rule. The accuracy of the ANN classification model was found satisfactory for learning data (95%) and testing data (82%).

The neural correlates of motor intentional disorders in patients with subcortical vascular cognitive impairment.

Subcortical vascular cognitive impairment (SVCI) refers to cognitive impairment associated with small vessel disease. Motor intentional disorders (MID) have been reported in patients with SVCI. However, there are no studies exploring the neuroanatomical regions related to MID in SVCI patients. The aim of this study, therefore, was to investigate the neural correlates of MID in SVCI patients. Thirty-one patients with SVCI as well as 10 healthy match control participants were included. A "Pinch-Grip" apparatus was used to quantify the force control capabilities of the index finger in four different movement phases including initiation, development, maintenance, and termination. All participants underwent magnetic resonance imaging (MRI). Topographical cortical areas and white matter tracts correlated with the performances of the four different movement phases were assessed by the surface-based morphometry and tract-based spatial statistics analyses. Poorer performance in the maintenance task was related to cortical thinning in bilateral dorsolateral prefrontal, orbitofrontal and parietal cortices, while poorer performance in the termination task was associated with the disruption of fronto-parietal cortical areas as well as the white matter tracts including splenium and association fibers such as superior longitudinal fasciculus. Our study demonstrates that cortical areas and underlying white matter tracts associated with fronto-parietal attentional system play an important role in motor impersistence and perseveration in SVCI patients.

The Effects of Age, Gender, and Hand on Force Control Capabilities of Healthy Adults.

OBJECTIVE: The present study examined the effects of age (20s to 70s), gender (male and female), and hand (dominant and nondominant) on force control capabilities (FCCs) in four force control phases (initiation, development, maintenance, and termination). BACKGROUND: Normative data of FCCs by force control phase are needed for various populations in age and gender to identify a type of motor performance reduction and its severity. METHOD: FCCs of 360 participants (30 for each combination of age group and gender) were measured using a finger dynamometer and quantified in terms of initiation time (IT), development time (DT), maintenance error (ME), and termination time (TT). RESULTS: Although gradual increases (1%~28%) by age were shown in IT, DT, and TT, a dramatic increase in ME was observed among participants in their 50s (26%), 60s (68%), and 70s (160%) compared to those in their 20s~40s. The most distinctive interaction effect of age and gender was found in ME out of the four FCC measures. Lastly, hand and its related interactions were not found significant. CONCLUSION: Normative FCC data were established for four age groups (20s~40s, 50s, 60s, and 70s) and gender. APPLICATION: The normative FCC data can be used for evaluating an individual's motor performance, screening patients with brain disorders, and designing input devices triggered and/or operated by the finger.

Development of a two-step touch method for website navigation on smartphones.

The touch method for hyperlink selection in smartphones can often create usability problems because a hyperlink is universally smaller than a finger contact area as well as visually occluded by a finger while pressing. In this study, we developed a two-step touch method (called Press and Flick method) and comprehensively examined its effectiveness using the goals, operators, methods, and selection rules (GOMS) model and user testing. The two-step touch method consisted of finger press and flick motions; a target hyperlink was selected by a finger press motion, and a finger flick method was subsequently conducted for error correction if the initial interaction (press) failed. We compared the two-step touch method with the current touch method through the GOMS model and user testing. As a result, the two-step touch method was significantly superior to the current touch method in terms of error rate and subjective satisfaction score; however, its superiority in terms of number of interactions and touch time was vulnerably affected by error rate. The two-step touch method developed in this study can improve the usability and user experience of website navigation using smartphones.

Effects of slanted ergonomic mice on task performance and subjective responses.

The biomechanical benefits (e.g., muscular activity) of slanted ergonomic mice have been comprehensively identified; however, their effects on task performance and subjective responses have not been fully investigated. The present study examined the effects of two slanted mice (slant angle = 30° and 50°) in comparison with a conventional mouse (slant angle = 0°) in terms of task performance (task completion time and error rate) and subjective responses (perceived discomfort score and overall satisfaction score). Experimental results showed that all of the task and subjective measures worsened as the slant angle of the target mice increases. For example, the task completion time (unit: ms) and overall satisfaction score (unit: point) of the 30° slanted mouse (time = 0.71, satisfaction = -0.09) and 50° slanted mouse (time = 0.73, satisfaction = -0.79) significantly deteriorated than the conventional mouse (time = 0.65, satisfaction = 1.21). The slanted mice seem to compromise biomechanical benefits with task performance and subjective responses.

Motor intentional disorders in vascular mild cognitive impairment and vascular dementia of subcortical type.

Subcortical vascular mild cognitive impairment (svMCI), a prodromal stage of subcortical vascular dementia (SVaD), is primarily associated with frontal injuries, whereas amnestic MCI (aMCI) is associated with temporoparietal injuries. Twenty-seven patients with svMCI, 20 with aMCI, 14 with SVaD, and 10 normal controls underwent motor intentional tasks (force initiation, development, maintenance, and termination) using a force dynamometer. Of the four motor intentional tasks, the maintenance task proved sensitive in differentiating svMCI from aMCI. In most motor intentional tasks, performances of svMCI patients were intermediate between those of controls and SVaD patients (initiation and termination: NC=aMCI=svMCI>SVaD; development: NC>aMCI=svMCI>SVaD; maintenance: NC=aMCI>svMCI=SVaD).

Directional and spatial motor intentional disorders in patients with right versus left hemisphere strokes.

OBJECTIVE: Motor intentional disorders (MIDs) are characterized by dysfunction in the preparation, initiation, maintenance, and termination of goal-oriented actions. In this study, we investigated (1) whether patients with right hemisphere strokes (RHS) and left hemisphere strokes (LHS) differ in the frequency of delayed action initiation (hypokinesia) and motor impersistence; (2) whether there is a directional or hemispatial component of hypokinesia or motor impersistence; (3) whether there is an association between the presence of hemispatial neglect and tests for MID; and (4) the location of injury associated with MID. METHOD: Thirty-two patients with acute unilateral stroke (21 with RHS and 11 with LHS) and 12 age-matched healthy controls participated in the study. To determine the presence and severity of directional and spatial hypokinesia and impersistence we used a new apparatus, the Directional Movement Tester (DMT). While being tested with the DMT, the participants held a static bar located either in the right or left hemispace using either their right or left hand and upon stimulus onset pushed the bar either leftward or rightward and maintained a given force for 10 sec. RESULTS AND CONCLUSION: The frequency of hypokinesia and impersistence was higher in the RHS group than in the LHS group, but there were no hypokinetic directional or spatial asymmetries. The RHS group did demonstrate left contralesional directional impersistence, but there were no spatial asymmetries of impersistence. Signs of hemispatial neglect were not associated with these measures of MID. Participants with frontal or subcortical lesions were significantly more likely to demonstrate hypokinesia and impersistence than those with posterior lesions.

An anthropometric analysis of Korean male helicopter pilots for helicopter cockpit design.

This study measured 21 anthropometric dimensions (ADs) of 94 Korean male helicopter pilots in their 20s to 40s and compared them with corresponding measurements of Korean male civilians and the US Army male personnel. The ADs and the sample size of the anthropometric survey were determined by a four-step process: (1) selection of ADs related to helicopter cockpit design, (2) evaluation of the importance of each AD, (3) calculation of required sample sizes for selected precision levels and (4) determination of an appropriate sample size by considering both the AD importance evaluation results and the sample size requirements. The anthropometric comparison reveals that the Korean helicopter pilots are larger (ratio of means = 1.01-1.08) and less dispersed (ratio of standard deviations = 0.71-0.93) than the Korean male civilians and that they are shorter in stature (0.99), have shorter upper limbs (0.89-0.96) and lower limbs (0.93-0.97), but are taller on sitting height, sitting eye height and acromial height (1.01-1.03), and less dispersed (0.68-0.97) than the US Army personnel. PRACTITIONER SUMMARY: The anthropometric characteristics of Korean male helicopter pilots were compared with those of Korean male civilians and US Army male personnel. The sample size determination process and the anthropometric comparison results presented in this study are useful to design an anthropometric survey and a helicopter cockpit layout, respectively.

Evaluation of the multivariate accommodation performance of the grid method.

The present study examined the multivariate accommodation performance (MAP) of the grid method, a distributed representative human models (RHM) generation method, in the context of men's pants sizing system design. Using the 1988 US Army male anthropometric data and ± 2.5 cm of fitting tolerance, the grid method selected two key dimensions (waist girth and crotch height) out of 12 anthropometric dimensions and identified 25 RHMs to accommodate 95% of the population. The average MAP of the RHMs decreased dramatically as the number of anthropometric dimensions considered increased (99% for single dimension and 14% for 12 dimensions). A standardized regression model was established which explains the effects of two factors (sum of anthropometric dimension ranges; adjusted R(2) between key dimensions and other anthropometric dimensions) on the MAP of RHMs. This regression model can be used to prioritize anthropometric dimensions for efficient MAP improvement of men's pants design.

Motor-intentional disorders in right hemisphere stroke.

OBJECTIVE: Damage to premotor and prefrontal regions results in motor-intentional disorders (MIDs) that disrupt initiation, maintenance, and termination of volitional movements. MIDs more frequently occur in right hemisphere rather than in left hemisphere injury. The aim of this study was to evaluate the prevalence of MIDs in patients with right hemisphere stroke and the factors that have influence on MIDs. METHODS: Subjects consisted of 25 consecutive patients with right hemisphere stroke and 12 normal controls. They underwent a series of experiments using force dynamometer along with bedside examination. RESULTS: It was identified that the force control test screened for MIDs with a higher sensitivity than bedside examinations: motor akinesia (38% vs. 11%), motor impersistence (50% vs. 10%), and motor perseveration (47% vs. 25%). The patients were significantly inferior to the controls in terms of force control capabilities in the 4 force control phases (1.6 to 16.3 times). The location and area of lesion and space of force production were not related to the severity of MIDs whereas the presence of neglect was related to the severity of MIDs. CONCLUSIONS: Our results suggest force dynamometer is a sensitive method to detect MIDs and the presence of neglect may influence the frequency of MIDs.

Determination of key dimensions for a glove sizing system by analyzing the relationships between hand dimensions.

The present study identified key dimensions for the development of a glove sizing system by analyzing the relationships between hand dimensions and demonstrated the construction process of glove sizing systems based on the selected key dimensions. Three hand dimensions (HL: hand length; HC: hand circumference; HB: hand breadth) were selected as the candidates of glove key dimensions by surveying the literature and industry practices of glove sizing systems. Of the key dimension candidates, HL and HC were selected by examining the results of correlation and multiple regression analyses on the 1988 US Army hand anthropometric data. A cross-tabulation of HL and HC with an interval length of 1.3 cm was constructed for each gender and the corresponding lengths and circumferences of cells covering more than 2% of the population were used to provide glove sizing parameters. It was identified that the glove sizing system for males is different from that for females and has more size categories.