• Safety and Health at Work
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• v.3 no.3
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• pp.192-198
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• 2012

Objectives: Slip and fall accidents in the workplace are one of the top causes of work related fatalities and injuries. Previous studies have indicated that fall risk was related to postural and dynamic stability. However, the usage of this theoretical relationship was limited by laboratory based measuring instruments. The current study proposed a new method for stability assessment by use of inertial measurement units (IMUs). Methods: Accelerations at different body parts were recorded by the IMUs. Postural and local dynamic stability was assessed from these measures and compared with that computed from the traditional method. Results: The results demonstrated: 1) significant differences between fall prone and healthy groups in IMU assessed dynamic stability; and 2) better power of discrimination with multi stability index assessed by IMUs. Conclusion: The findings can be utilized in the design of a portable screening or monitoring tool for fall risk assessment in various industrial settings.

• Journal of Institute of Convergence Technology
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• v.10 no.1
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• pp.41-45
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• 2020

This paper presents the effects of a virtual mass on the stability boundary of a virtual spring in the haptic system with first-order-hold. The virtual rigid body is modeled as a virtual spring and a virtual mass. When first-order-hold is applied, we analyze the stability boundary of the virtual spring through the simulation according to the virtual mass and the sampling time. As the virtual mass increases, the stability boundary of the virtual spring gradually increases and then decreases after reaching the maximum value. The results are compared with the stability boundary in the haptic system with zero-order-hold. When a virtual mass is small, the stability boundary of a virtual spring in the system with first-order-hold is larger than that in the system with zero-order-hold.

• 제어로봇시스템학회:학술대회논문집
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• 1988.10b
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• pp.1006-1013
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• 1988

We have shown how unstructured modeling was used to derive a general stability condition in Part 1. In Part 2, we focus on the particular dynamics (structures modeling) of the robot manipulator and environment. Using rigid body dynamics, the stability condition for the direct drive robots has been achieved in terms of the Jacobian and robot tracking controller. Combining the structured and unstructured modeling, a stability condition for a particular application can be obtained. This approach has been used to analyze compliant motion on the University of Minnesota robot using a feedforward torque controller. We have obtained a stability condition for this application. Through both simulation and experiment, the sufficiency of this condition has been demonstrated. For a sufficient stability condition, recall that if the condition is satisfied, then the stability is guaranteed; however, if the condition is violated, no conclusion can be made.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.38 no.11
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• pp.950-957
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• 1989

We have shown how unstructured modeling was used to derive a general stability condition in Part 1. In Part 2, we focus on the particular dynamics (structured modiling) of the robot manipulator and environment. Using rigid body dynamics, the stability condition for the direct drive robots has been achieved in terms of the Jacobian and robot tracking controller. Combining the structured and unstructured modeling, a stability condition for a particular application can be obtained. This approach has been used to analyze compliant motion on the University of Minnesota robot using a feedforward torque controller. We have obtained a stability condition for this application. Through both simulation and experiment, the sufficiency of this condition has been demonstrated. For a sufficient stability condition, recall that if the condition is satified, then the stability is guaranteed` however, if the condition is violated, no conclusion can be made.

• Physical Therapy Korea
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• v.6 no.1
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• pp.35-46
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• 1999

The purposes of this study were to evaluate and compare the limits of stability(LOS) at different body positioning(standing and one leg standing) in normal 20 years of age. Fourty subjects participated in the study. Subjects comprised 20 males and 20 females who without neurologic, orthopaedic impairments and balance performance impaired. The LOS was measured at Two Feet Forceplate and One Leg Forceplate with BPM(Balance Performance Monitor) Dataprint Software Version 5.3. The subjects stood 4 inches between the feet at Two Feet Forceplate and stood one legged at One Leg Forceplate. In this study applied the paired t-test and independent t-test to determine the statistical significance of results at 0.01 and 0.05 level of significance. The results of this study were as follows: 1) The anteroposterior LOS significantly increased with one legged stance(p<0.05). 2) The mediolateral LOS significantly decreased with one legged stance(p<0.01). 3) There were significant difference posterior LOS in standing and anterior LOS in one legged stance according to sexual difference(p<0.05). 4) The mediolateral LOS was not significant difference between standing and one legged stance according to sexual difference(p>0.05).

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.9
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• pp.843-850
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• 2007

This paper proposes a somatosensory stimulation system for the improvement of postural stability using vibration as somatosensory stimulation. This system consists of vibratory stimulation and postural response measurement. To evaluate this system, the center of pressure(COP) was closely observed in turn with simultaneous or separate mechanical vibratory stimulations to flexor ankle muscles (tibialis anterior, triceps surae) and two plantar zones on both feet while standing on a stable and an unstable support. The simultaneous vibratory stimulations cleared influenced postural stability and the effects of vibrations were higher with the unstable support. In separate vibratory stimulations, the extent of the COP sway reduced when the direction of the vibratory stimulations and that of the inclination of body coincided for flexor ankle muscle stimulations. In the contrary, the extent of the COP sway increased when the direction of the stimulations and that of body inclination coincided for plantar zone stimulations. These results can be useful for the development of rehabilitation systems that utilizes somatosensory inputs for postural balance.

• Journal of Biomedical Engineering Research
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• v.28 no.5
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• pp.628-635
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• 2007

We studied the effect of vibratory stimulations of different leg muscles, tibialis anterior(TA) and triceps surae(TS), and plantar zones in ten healthy subjects during 1) quiet standing, 2) forward lean of body, 3) backward lean of body, 4) right lean of body, and 5) left lean of body. The experiments were performed on the force platform. The effect of vibration were measured by monitoring the area of COP(Center of pressure) sway. The subjects wore a vibratory stimulation system on foot and ankles and were given the instruction not to resist against the applied perturbations. The results show that all vibratory stimulations to lower limb muscles and plantar zones reduced the COP sway area. This reduction of the COP sway area occurred also in partial vibratory stimulations during quiet standing. In forward lean of body, vibratory stimulations to TA reduced the COP sway area. During backward lean of body, vibratory stimulations to TS reduced the COP sway area. When the subject was tilted right, vibratory stimulations to left plantar zone reduced the COP sway area. During left lean of body, vibratory stimulations to right plantar zone reduced the COP sway area. Thus, the influence of vibratory stimulations to leg muscle and plantar zones differed significantly depending on the lean of body. We suggest that the vibration stimuli from leg muscles and plantar zones could be selectively used to help maintaining postural balance stable.

• Geomechanics and Engineering
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• v.32 no.2
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• pp.145-157
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• 2023

This paper aims at investigating the face stability of large-diameter underwater shield tunnels considering seepage in soft-hard uneven strata. Using the kinematic approach of limit upper-bound analysis, the analytical solution of limit supporting pressure on the tunnel face considering seepage was obtained based on a logarithmic spiral collapsed body in uneven strata. The stability analysis method of the excavation face with different soft- and hard-stratum ratios was explored and validated. Moreover, the effects of water level and burial depth on tunnel face stability were discussed. The results show the effect of seepage on the excavation face stability can be accounted as the seepage force on the excavation face and the seepage force of pore water in instability body. When the thickness ratio of hard soil layer within the excavation face exceeds 1/6D, the interface of the soft and hard soil layer can be placed at tunnel axis during stability analysis. The reliability of the analytical solution of the limit supporting pressure is validated by numerical method and literature methods. The increase of water level causes the instability of upper soft soil layer firstly due to the higher seepage force. With the rise of burial depth, the horizontal displacement of the upper soft soil decreases and the limit supporting pressure changes little because of soil arching effect.

• 제어로봇시스템학회:학술대회논문집
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• 1988.10a
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• pp.113-118
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• 1988

The problem of controlling static gaits of a Quadruped Walking Robot is investigated. A theoretical approach to the gait study is proposed in which the static stability margins for periodic gaits are expressed in terms of the kinematic gait formula. The effects of the stride length to the static stability are analyzed, and the relations between the static stability and the initial body configurations are examined. Extensive computer simulations are performed to verify the analysis results.

• Archives of design research
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• v.20 no.3 s.71
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• pp.5-14
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• 2007

The purpose of this study is to investigate the effects of personal characteristics and body cathexis of middle-aged women on their clothing image preferences. Data was collected using questionnaire from 35 to 59 of age living in Daegu. The questions for personal characteristics included ascendancy, responsibility, emotional stability, sociability and self-confidence. Clothing images included the noble, bold, practical and female. Data were analyzed using SAS, SPSS programs for frequency, percentage, average, correlation, ANOVA, Duncan's multiple range test. The results of this study are as follows: 1. The body cathexis of middle-aged women to their own body is not so high and the satisfaction with their body parts were face features, upper limb, lower limb, torso, height, physique, weight orderly. 2. The more satisfied with their body the higher emotional stability and self-confidence. 3. The more satisfied with the face the more preferred noble, bold, female image in doffing. The more satisfied with the torso and physique the more preferred bold, female image in clothing. 4. Middle-aged women with a high ascendancy preferred bold image and, those with a high responsibility preferred a practical image. Those with a high emotional stability preferred noble, practical image. Middle-aged women having a high sociability preferred noble, male image and having a high self-confidence preferred bole, male image.