• Journal of the Korean Society for Precision Engineering
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• v.23 no.4 s.181
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• pp.75-82
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• 2006

In this paper, we propose an optimal trajectory for biped robots to move up-and-down stairs using a genetic algorithm and a computed-torque control for biped robots to be dynamically stable. First, a Real-Coded Genetic Algorithm (RCGA) which of operators are composed of reproduction, crossover and mutation is used to minimize the total energy. Constraints are divided into equalities and inequalities: Equality constraints consist of a position condition at the start and end of a step period and repeatability conditions related to each joint angle and angular velocity. Inequality constraints include collision avoidance conditions of a swing leg at the face and edge of a stair, knee joint conditions with respect to the avoidance of the kinematic singularity, and the zero moment point condition with respect to the stability into the going direction. In order to approximate a gait, each joint angle trajectory is defined as a 4-th order polynomial of which coefficients are chromosomes. The effectiveness of the proposed optimal trajectory is shown in computer simulations with a 6-dof biped robot that consists of seven links in the sagittal plane. The trajectory is more efficient than that generated by the modified GCIPM. And various trajectories generated by the proposed GA method are analyzed in a viewpoint of the consumption energy: walking on even ground, ascending stairs, and descending stairs.

• Journal of architectural history
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• v.9 no.1 s.22
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• pp.47-64
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• 2000

The Chapel and Exhibition hall of Chul-du-san-Holy place are considered as the most important work of architect Lee Hee-Tai (1925-1980), and as a work representing Korean architecture in 1960's. What is the reason that these buildings can acquire such a remarkable estimation? This study tries to make clear this reason with an analytic method. These buildings are situated in singular site, in which small mountain comes up alongside with Han-river. Architect laid out the Chapel and Exhibition hall to the memory of 108 saints who died for their faith in this mountain, considering the specificity of the site, the direction of approach stair, and the formation of public space. Architect proposes an opposed composition of form for these two buildings. So the Exhibition hall is characterized by trabeated structure, centripetal force and Apollonian order. It has strictly proportioned facade, which is composed of two 15m-by-l5m squares and subdivided equally in three portions. The Chapel is charaterized by arcuated structure, centrifugal force, and Dionysosian sentiment. In this work, architect Lee Hee-Tai also expressed the locality of Korean architecture with the grammar of column-roof.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.387-392
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• 2000

In cementless total hip replacement(THR), an initial stability of the femoral component is important to long term fixation of femoral stem. The initial stability has close relationship with the relative displacement of prosthesis and spongy bone at the proximal of femur. After implantation of the prosthesis. the surrounding bone is partially shielded from load carrying and starts to resort. Stress shielding is the cause of the loss of proximal bone. Assessing stress distribution of femur is important to predict stress shielding. The initial stability and the stress shielding were investigated for two loading conditions approximating a single leg stance and a stair climbing. Three types of stems were studied by the finite element method to analyze the biomechanical effects of distal filling of cementless femoral stems, Three types of stems employed are a distal filling stem, a distal flexible stem, and a distal tapered stem.

• Journal of KIBIM
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• v.7 no.4
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• pp.21-30
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• 2017

Due to the rapidly aging population, the death rate of elderly people by safety accidents has been increasing. In particular, precautions are needed for falls prevention because they either directly or indirectly cause death. In the case of elderly people, most of the fall accidents occur in dense residential areas, and particularly, the staircase poses a risk of falling. Therefore, a safety assessment should be performed from the design phase. However, in general, staircases are designed using existing stair data or only aims to satisfy the installation criteria. Laws and regulations only define minimum requirements for safety, so it is not possible to prevent fall accidents even if they satisfy the requirements. Therefore, this study proposes a simulation-based method for evaluating the safety of staircases. The behavioral characteristics of the elderly are implemented to an virtual user in a virtual space including staircases, and fall accidents are evaluated by the evaluation logic related to the behavioral characteristics. The result shows that the safety of staircases can be preevaluated and reflected on the design to reduce the possibility of fall accidents of the elderly.

• Journal of the Korean Society of Clothing and Textiles
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• v.30 no.5 s.153
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• pp.779-787
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• 2006

Pantyhose is a close-fitting garment. Consumers are highly sensitive to any progress done in fitting their lower body and increasing comfort. However, pantyhose manufactured in Korea are only one-sized. The purpose of this study is to suggest the size designation of pantyhose, using new human body measurement data which were gained from the Year 2004 SIZE KOREA project. For the purpose of this study, the ISO standards and JIS standards were reviewed and questionnaire was carried out to manufacturers and distribution companies. The results are as follows: First, for a difference with size standards established in 2002, applicable age range was expanded from 15 to 70 year-old women to entirely include persons who wear panty hose. Secondly considering the actual condition that panty hose is producing in single size in most companies due to its elasticity of material, number of size was reduced from five to four. Thirdly basic parts of body which were applied to panty hose are height and hip girth. And size of panty hose is decided by a chart which is composed of height-axis and hip-axis.

• Korean Institute of Interior Design Journal
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• v.14 no.3 s.50
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• pp.147-155
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• 2005

As multiplex theaters are increasing rapidly in number, concerns over the evacuation process in case of fire emergency are also increasing. The study investigates the users' awareness and recognition of evacuation route by the method of questionnaire, and analyzes the users' behavior in choosing the route by the simulation program called Simulex. Among others, findings indicate a vast majority of the users are unaware of the proper route in the emergency, yet anticipate to evacuate by it, instead of the entry/exit route that they are familiar with. This aspect, however, can be useful to provide the proper route of evacuation for the users, if an appropriate information is given that the entry/exit route is also used as an emergency egress. The simulation shows heavy congestion at the closer evacuation route from the exit, and distinctly less traffic at the farther means of egress. Based on this natural phenomenon, it is suggested that the emergency stair should be nearby and aligned with the exit from auditorium. Although the present building regulation only requires a minimum dimension at each route, there is a need to widen the passageway that is likely to be recognized easily and subsequently overcrowded in case of fire emergency.

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.2
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• pp.184-191
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• 2009

The common requirements of rough terrain mobile robots are long-term operation and high mobility in rough terrain to perform difficult tasks. In rough terrain, excessive wheel slip could cause an increase in the amount of dissipated energy at the contact point between the wheel and ground or, even more seriously, the robot could lose all mobility and become trapped. This paper proposes a traction control algorithm that can be independently implemented to each wheel without requiring extra sensors and devices compared with standard velocity control methods. The proposed traction algorithm is analogous to the stick-slip friction mechanism. The algorithm estimates the slippage of wheels by angular acceleration change, and controls the increase or decrease state of torque applied to wheels Simulations are performed to validate the algorithm. The proposed traction control algorithm yielded a 65.4% reduction of total slip distance and 70.6% reduction of power consumption compared with the standard velocity control method.

• The Journal of Korea Robotics Society
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• v.18 no.2
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• pp.182-188
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• 2023

Due to the acceleration of an aging society, the need for lower limb exoskeletons to assist gait is increasing. And for use in daily life, it is essential to have technology that can accurately estimate gait phase even in the walking environment and walking speed of the wearer that changes frequently. In this paper, we implement an LSTM-based gait phase estimation learning model by collecting gait data according to changes in gait speed in outdoor level ground and stair environments. In addition, the results of the gait phase estimation error for each walking environment were compared after learning for both max hip extension (MHE) and max hip flexion (MHF), which are ground truth criteria in gait phase divided in previous studies. As a result, the average error rate of all walking environments using MHF reference data and MHE reference data was 2.97% and 4.36%, respectively, and the result of using MHF reference data was 1.39% lower than the result of using MHE reference data.

• Journal of Korean Physical Therapy Science
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• v.11 no.3
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• pp.28-37
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• 2004

Background: Lumbar joint dysfunction is reported to be the main cause of lower back pain (LBP). The purpose of this study was to evaluate the effect of joint dysfunction on the postural balance of the lower hack and pelvis in different normal activities such as walking or stair management. Also it was studied whether the status of LBP (intensity and duration of LBP, length of treatment) contributes to die pelvic height difference (PHD) in various postures. Subjects: 28 patients with LBP and 32 normal adult volunteers, 60 years of age or younger, who came to the Community Health Center and orthopedic clinics in Incheon, South Korea. Methods: In order to determine the accuracy of the manual angulometer method in measuring the PHD, it was compared to the pelvic x-ray method in selected subjects. In the manual angulometer method, the arm of the angulometer was placed on the top of both iliac crests. The PHD was measured in static upright stance, then one-legged stance, on the affected leg or unaffected leg each time. Information regarding the disease status was obtained through interviews. Visual assessment scale was used to grade the intensity of LBP. Data analysis was performed using SPSS 10.0/PC program. Homogeneity between the two groups was tested by 2-test and t-test. To compare the PHD of the subgroups, we used t-test, F-test and two-way ANOVA. Relationships among dependent variables were analyzed by Pearson correlation analysis. Conclusion: In patients with LBP, lumbar joint dysfunction causes lumbar and pelvic postural asymmetry during normal activities.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.1
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• pp.149-158
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• 2004

In most RP processes, the inherent stair-stepped surfaces and shrinkage-induced warping of the parts require post processing such as surface finishing. To minimize such defects, VLH-ST, a newly developed RP process, employs a 3.9-mm thick expandable polystyrene (EPS) foam sheet and a hot wire to contour it to have slant linear-interpolated sides. The use of relatively thick sheets for layers, however, limits the process capability of constructing fine details, especially smaller than the layer thickness. This study is focused on the development of a post processing method fo fine details of VLM-ST parts. The post-processing tool was designed to meet all the requirements for the desirable post processing. It adopted a hot wire as a means of melting the EPS foam sheet. Various basic experiments on the post processing were carried out to obtain the optimal process conditions. The dominant process parameters such as the radiated heat input, the tool speed, and the gap between the tool tip and the foam sheet (tool height) were considered in the experiments. The effectiveness of the developed post-processing method fo forming or engraving fine details on the VLM-ST parts has been thus demonstrated. The experiments on engraving several sets of letters, such as CANESM, 인간, and 한국과학기술원, on the EPS foam sheet were carried out. In addition, a flowery shape was engraved on a three-dimensionally curved surface of a pottery-shape VLM-ST part.