• The Journal of Korean Physical Therapy
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• v.21 no.2
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• pp.97-101
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• 2009

Purpose: This study examined how the direction of carrying a load affects the foot stability and kinesiology while walking. Methods: The heel rotation, Hallux stiffness, foot balance, metatarsal load, toe out angle, subtalar joint flexibility were measured in 40 adults (men and women) who carried a load back and forth, walking on a 2-meter-long board. The measurement was carried out three times and the mean of the measurements was used to compare the difference between the front, back and the condition without a load. Results: While walking, heel rotation and hallux stiffness occurred most when a front load was applied compared to a back load or no load condition (p<0.05). A metatarsal load also appeared to be the highest with the frond load, but there was no significant difference in the balance of the whole foot. Both the toe out angle and subtalar joint flexibility appeared to increase significantly (p<0.05). Conclusion: Applying the front load causes subtalar joint instability and increases the plantar foot pressure imbalance during walking.

• Proceedings of the KSR Conference
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• 2005.05a
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• pp.115-122
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• 2005

This study analyzed the characteristics of four kinds of bridge rubber pads and suggested how to determine the stiffness the pads. The stiffness of rubber pads can be estimated by a direct static test. In the procedure to estimate the stiffness of a pad, the dead load(preload) of a bridge and live load of a vehicle are considered. The polyurethane rubber pads have larger hardness than natural and chloroprene rubber pads and thus carry larger load bearing capacity. In addition, they showed higher stiffness with the same shape factor than the others and thus are more avaliable as for bridge bearings. Although natural and chloroprene rubber pads are elongated to large deformation in horizontal direction due to vertical loads, polyurethane rubber pads almost do not generate horizontal deformation due to vertical loads regardless to the thickness and hardness of the pads. Therefore, they do not need reinforced plate to restrict horizontal deformation.

• Journal of Korean Association for Spatial Structures
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• v.16 no.2
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• pp.89-96
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• 2016

Cable structures are lightweight structures of flexible type, cable members have only axial stiffness related to tension, they can carry neither bending nor compression. This study is the analysis of cable truss systems are composed of upper and low cables by connecting bracing cables, the structural principle is based on a tensegrity system by using bracing tension members, discontinuous compression members and continuous tension members. A hanging roof of cable truss system is too flexible against vertical loads, most cable members are stabilized by connecting the prestressed upper and lower cable by bracing cables. A cable truss roof system is formed by adding a set of cables with reverse curvature to the suspension cables. With the sets of cables having opposite curvature to each other, cable truss is able to carry vertical load in both upward and downward direction with equal effectiveness, and then a cable truss acts as load bearing elements by the assemble of ridge cables, valley cables and bracing cables. This paper will be shown the geometric non-linear analysis result of cable truss systems with various sag ratio for deflections and tensile forces, the analytical results are compared with the results of other researchers.

• Proceedings of the KSR Conference
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• 1998.11a
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• pp.47-53
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• 1998

Many kinds of methods have been developed to carry out transverse analysis of prestressed concrete(PSC) box girder bridges. However, most bridge engineers only use the simple frame model to analyze PSC box girder in transverse direction because of its simplicity and easy usage. But, this frame model has many problems such that it can't consider warping, distortion and longitudinal load distribution. In this study, the results from simple frame model and 3-dimensional shell model with UIC load are compared to show its validity. The results from frame model are slightly larger than those of shell model in symmetric loading case. But, positive bending moment of top slab is larger in shell model than frame model in case subject to anti-symmetric loading. It shows that simple frame model can't always give conservative results, so a practical tool whose treatment is easy and whose product is reliable shall be developed as soon as possible.

• Journal of Korean Association for Spatial Structures
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• v.17 no.1
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• pp.31-40
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• 2017

The objective of this study is to analysis the mechanical characteristics and nonlinear behaviors on the geometric nonlinear behavior of a cable spoke wheel roof system for long span lightweight roof structures. The weight of a cable spoke wheel roof dramatically can reduce and the cable roof system can easily make the required rigidity and shape by the sag ratio and pretension forces. Determining the pretension and initial sag of cable roof system is essential in a design process and the shape of roof is changed by pretension. The nonlinear behavior of flexible cable system has greatly an affect on the sag and pretension. This paper will be carried out analyzing and comparing the tensile forces and deflection of a cable spoke wheel system for the large span retractable roof, and analyzed to deflections and tensile forces by the post height of center hub. The double arrangement of a spoke wheel system with reverse curvature works more effectively as a load bearing system, the pretension can easily increase the structural stiffness. The cable truss system can carry vertical load in up and downward direction, and act effectively as load bearing elements.

• Steel and Composite Structures
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• v.34 no.2
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• pp.299-308
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• 2020

This study aims to carry out the experimental and numerical investigation on the flexural behavior of sandwich honeycomb composite (SHC) beams reinforced with novel triaxially woven fabric composite skins. Different stacking sequences of the carbon fiber reinforcement polymer (CFRP) laminate; i.e., 0°-direction of TW (TW0), 0°-direction of UD (UD0), and 90°-direction of UD (UD90) were studied, from which the flexural behavior of SHC beam behaviors reinforced with TW0/UD0 or TW0/UD90 novel laminated skins were compared with those reinforced with UD0/90 conventional laminated skins under four-point loading. Generally, TW0/UD0 SHC beams displayed the same flexural stiffness as UD0/90 SHC beams in terms of load-deflection relationships. In contrast, TW0/UD90 SHC beams showed a 70% lower efficiency than those of UD0/90 SHC. Hence, the TW0/UD0 laminate arrangement is more effective with a mass reduction of 39% compared with UD0/90 for SHC beams, although their stiffness and shear strength are practically identical.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.6
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• pp.1235-1241
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• 2012

In this paper, each driving motor for leg joints on a robot is controlled by estimating the direction of the legs measuring each joint angle and attitude angle of robot. We used quadruped working robot named TITAN-VIII in order to carry out this experimental study. 4 load cells are installed under the bottom of 4 legs to measure the pressed force on each leg while it's walking. The walking experiments of the robot were performed in 8 different conditions combined with duty factor, the length of a stride, the trajectory height of the foot and walking period of robot. The validity of attitude control for quadruped walking robot is evaluated by comparing the pressed force on a leg and the power consumption of joint driving motor. As a result, it was confirmed that the slip-condition of which the foot leave the ground late at the beginning of new period of the robot during walking process, which means the attitude control of the robot during walking process wasn't perfect only by measuring joint and attitude angle for estimating the direction of the foot.

• Journal of the Ergonomics Society of Korea
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• v.34 no.4
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• pp.313-326
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• 2015

Objective: The objective of this research is to quantitatively analyze muscle activities of arm and shoulder, according to direction in various types of one-handed manual material handling, based on surface electromyography. Background: Workers in industrial sites frequently carry out one-handed manual material handling using arm and shoulder muscles. Therefore, chronic load and accumulated fatigue occur to arm and shoulder muscles, which becomes a main cause of upper arm and shoulder musculoskeletal disorders. The shoulder muscles have widely range of motion, and complex interactions take place among various muscles including rotator cuff muscles. In this regard, research on interactions among should muscles, according to such various dynamic motions, is required. Method: Ten male subjects in their 20s participated in this research. This research considered upward, downward, leftward, rightward, forward and backward directions and fourteen muscles around arm and shoulder (biceps brachii and trapezius, etc.) as independent variables. The mean muscle activity was set as the dependent variable. This research extracted $4^{th}{\sim}7^{th}$ repetition signals according to ten times of repetitive muscle contraction, and analyzed the muscle activity concerned using the envelope detection technique. Results: The mean muscle activity of upward direction was analyzed highly statistically significant. The reason is that the effect of gravity works to arm and shoulder muscles. Also, it is conjectured that deformation of coracoacromial ligament was caused, and its contact pressure increased, due mainly to the shoulder flexion, and therefore load was analyzed high. Muscle activity was analyzed significantly low, according to concentric ballistic motion used in the concentric contraction phase by storing elastic energy in the eccentric contraction phase with a motion to bring the weight to the front of subject's body as to downward, leftward and backward directions. Because, elbow joint's flexion-extension motions mainly occurred, biceps brachii was analyzed high muscle activity as the prime mover. Conclusion: The information on the quantitative load of muscles can be applied to ergonomic work design for one-handed manual material handling to minimize muscle load. Application: This research has effectively identified muscle activity according to dynamic contraction by applying an envelope detection technique. The results can be used for ergonomic work design to minimize muscle load during the one-handed manual material handling, according to each direction. The research results are expected to be used for musculoskeletal disorder prevention and physiotherapy in the rehabilitation medical field, based on the muscle load of arm and shoulder in various directions.

• Physical Therapy Rehabilitation Science
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• v.9 no.1
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• pp.36-42
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• 2020

Objective: Many caregivers often carry infants using baby carriers until they are approximately 36 months old. The purpose of this study was to compare the muscular activity of the trunk and lower leg muscles during trunk flexion-extension movements in correspondence to various wearing methods of a baby carrier blanket. Design: Cross-sectional study. Methods: Sixteen healthy adult women were to wear baby carrier blankets in five different ways in terms of direction and height, followed by flexion-extension of the trunk. Erector spinae (ES), rectus abdominis, rectus femoris (RF), biceps femoris (BF) muscle activities and triaxial acceleration of trunk were investigated. Results: The front-wearing method of the baby carrier blanket increased the muscular activity of the ES muscle, and wearing the baby carrier blanket at waist height in the same direction was significantly higher than wearing it at pelvic height (p<0.05). As the angle of flexion increased during trunk flexion-extension, the muscle activity of the ES, BF, and the RF increased. There was a greater increase in muscle activity of the ES and the BF during extension compared to flexion (p<0.05). Conclusions: If it is difficult to wear a baby carrier blanket due to lumbar pain, it is recommended to lower the wearing height of the baby carrier to the pelvic level so that the external load can be transferred to the lower extremity. In addition, it appears to be necessary to hold the baby and distribute the load onto the waist through proper body control when performing flexion-extension movements of the trunk. More objective and scientific research that includes various daily tasks and evaluation methods are needed.

• Journal of Korean Association for Spatial Structures
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• v.17 no.2
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• pp.21-32
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• 2017

The objective of this study is to analysis the mechanical characteristics on the geometric nonlinear behavior of radial cable roof systems for long span retractable cable roof structures. The retractable roof is designed as a full control system to overcome extreme outdoor environments such as extreme hot or cold weather, strong wind or sunlight, and the cable roof greatly can reduce roof weight compared to other rigid structural system. A retractable cable roof system is a type of structures in which the part of entire roof can be opened and closed. The radial cable roof is an effective structural system for large span retractable roofs, the outer perimeter of the roof is a fixed membrane roof and the middle part is a roof that can be opened and closed. The double arrangement cables of a radial cable truss roof system with reverse curvature works more effectively as a load bearing cables, the cable system can carry vertical load in up and downward direction. In this paper, to analyze the mechanical characteristics of a radial cable roof system with central posts, the authors will investigate the tensile forces of bearing cables, stabilized cables, ring cables, and the deflection of roof according to the height of the post or hub that affects the sag ratio of cable truss. The tensile forces of the cables and the deflection of the roof are compared for the cases when the retractable roof is closed and opened.