• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.10a
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• pp.258-263
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• 2009

This paper describes an analysis of the stability and performance of a large-capacity flywheel energy storage system (FESS) supported by active magnetic bearings. We designed and manufactured the system that can store up to 5kWh of usable energy at the maximum speed of 18,000 rpm. In order to analyze the stability of the systems accurately, we derived a rigid body rotor model, flexible rotor model using finite-element method, and a reduced-order model using modal truncation. The rotor model is combined with those of active magnetic bearings, amplifiers, and position sensors, resulting in a system simulation model. This simulation model is validated against experimental measurements. The stability of the system is checked from the pole locations of the closed-loop transfer functions. We also investigated the sensitivity function to quantify the robustness of the systems to the disturbances such as mass imbalance and sensor noises.

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.3
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• pp.233-239
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• 2013

This paper presents the analysis and control of the position of the COG (Center of Gravity) for a two-wheel balancing robot. The two-wheel balancing robot is required to maintain balance by driving two wheels only. Since the robot is not exactly symmetrical and its dynamics is changing with respect to moving parts, robust balancing control is difficult. Balancing performance becomes difficult when two arms hold a heavy object since the center of gravity is shifted out of the wheel axis. Novel design of a sliding waist mechanism allows the robot to react against the shift of the COG by moving the whole upper body to compensate for the imbalance of the mass as a counter balancer. To relocate the COG position accurately, the COG is analyzed by force data measured from two force sensors. Then the sliding COG mechanism is utilized to control the sliding waist position. Experimental studies are conducted to confirm the proposed design and method.

• Korean Journal of Applied Biomechanics
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• v.26 no.2
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• pp.213-220
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• 2016

Objective: The purpose of this study was to investigate the effect of an 8-week ProBody massage program on body alignment and plantar pressure balance in middle-aged men with musculoskeletal diseases. Method: The subjects of this study were 20 middle-aged men with musculoskeletal diseases in B Metropolitan City who participated in an 8-week ProBody massage program conducted twice a week. Physical characteristics (height, weight, and body mass index), body alignment, and plantar pressure were assessed before and after the experiment. Results: The 20 middle-aged men with musculoskeletal diseases who underwent the ProBody massage program showed positive changes in physiological characteristics, body alignment, and plantar pressure balance. Conclusion: Consequently, the 8-week ProBody massage program was suggested to be effective for improving and preventing postural imbalance in middle-aged men with musculoskeletal diseases. The ProBody massage program could also be utilized to improve the body alignment and plantar pressure balance in middle-aged women with musculoskeletal diseases.

• Journal of Nutrition and Health
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• v.32 no.6
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• pp.713-725
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• 1999

Women have a greater incidence of coronary heart disease(CHD) after menopause. It relates to hormone imbalance-induced changes in known CHD risk factors, especially hyperlipidemia. Accordingly, once women are diagnosed, the rate of morbidity and mortality is greater than for men. Thus, preventive strategies are critical to improve the quality oflife in the later years for women. The purpose of ths study was to explore the difference of anthropometric, environmental factors and food behaviors between normocholesterolemia and hypercholesterolemia within postmenopausal women. The subjects were classified as normocholesterolemia and hypercholesterolemia based on the Guideline for Korean Hyperlipidemia. The results obtained are summarized as follows. The distributions of general characteristics such as age, family income, occupation status, age at menarche, and menopausal period were not significantly different between the normocholesterolemia group and hypercholesterolemia group. The anthropometric factors such as body mass index(BMI) and waist hip ratio(WHR) were not significantly different between the normocholesteroemia group and the hypercholesterolemia group but odds ratio of hypercholesterolemia group was higher than that of normocholesterolemia but not significant. Aerobic activity more than 1hours/day was significantly related to low serum cholesterol concentration. Eating behaviors related to regular meal time, regular breakfast habit, and slow meal speed were related to low serum cholesterol concentration. Eating the chicken without skin was significantly related to low serum cholesterol concentration. Our data indicate that desirable eating habit, aerobic activity more than 1hr/day are important factors of serum cholesterol concentrations in postmenopausal women. The result of this study provide information that is important in designing appropriate dietary guidelines for hypercholesterolemia in postmenopausal women.

• Journal of computational fluids engineering
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• v.18 no.3
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• pp.51-59
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• 2013

A significant change in aerodynamic characteristics of wind turbine blade can occur by ice formed on the surface of the blade operated in cold climate. The ice accretion can result in performance loss, overloading due to delayed stall, and excessive vibration associated with mass imbalance. In this study, the impact of ice accretion on the aerodynamic characteristics of NREL 5MW wind turbine blade sections is examined by a CFD-based method. It is shown that the thickness of ice accretion increases from the root to the tip and the effects of icing conditions such as relative wind velocity play a significant role in the shape of ice accretion. In addition, the computational results are used to assess the degradation in the lift and drag coefficients of the blade sections.

• Korean Journal of Applied Biomechanics
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• v.27 no.1
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• pp.59-66
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• 2017

Objective: This study investigated the effect of a 16-week upright body exercise program on body balance and plantar pressure balance in elderly women. Method: The subjects included elderly women in B Metropolitan city who participated in an upright body exercise program twice weekly for 16 weeks. The subjects' physical characteristics (height, weight, body mass index [BMI]), posture balance, and foot plantar pressure were measured before and after the experiment. Results: The upright body exercise program showed positive changes in posture balance and foot plantar pressure balance in seven elderly women. Conclusion: The second version of the upright body exercise program improved and may prevent postural imbalance in elderly women. This program could be utilized to improve posture and foot balance in elderly persons.

• Journal of The Korean Society of Agricultural Engineers
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• v.51 no.1
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• pp.33-39
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• 2009

A number of fallow paddies field continues to increase because of adverse agricultural circumstance such as upsurge income of foreign products, increase of labor costs in local community, imbalance between productivity and profitability etc. Such fallow paddies are necessary to be protected against weeds and trees. If fallow paddies are not managed, it will be devastated and needed cost for re-cultivation. Therefore, management of gradually increased fallow paddy fields should be conducted. In this study, the effect of plants growth inhibition and water quality purification through the control of flood in fallow paddy were examined in an experimental field. The managed and unmanaged fallow paddies through the control of water depth were constructed in the experimental field. The monitoring was conducted from 2005 to 2007. As the result, the managed fallow paddies were more effective than the unmanaged ones on the growth inhibition and water purification. In addition, when the fallow paddy is managed with regular water depth, it was the most effective in the plants growth inhibition.

• Journal of the Korean Society of Food Science and Nutrition
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• v.37 no.1
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• pp.16-19
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• 2008

Bone mass in adults decreases with age because of the imbalance between the rate of bone formation and resorption. We performed this study to investigate whether Asparagus cochinchinensis (Lour.) Merr. (ACAE) plays a role in osteoblasts differentiation and osteoclasts formation. Ethanol extract of ACAE showed increase in the differentiation and alkaline phosphatase activity of osteoblasts. Also, it decreased the number of tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells (OCLs) and TRAP activity. Therefore, ACAE has the potential to prevent bone-related diseases such as osteoporosis by increasing the differentiation of osteoblasts and reducing both the number and activity of osteoclasts.

• Proceedings of the KIEE Conference
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• 2005.04a
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• pp.277-279
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• 2005

The imbalance of energy demand and supply caused by rapid industrialization around the world and the associated environmental issues require and alternative energy source with possible renewable fuels. Political instability and depletion of cruel oils are other factors that cause fluctuation of oil price. Securing a new alternative energy source for the next century became an urgent issue that our nation is confronting with. As a matter of fact, the fuel cell technology can be widely used as next generation energy regardless of regions and climate. Specially, the ability of expansion and quick installation enable one to apply it for distributed power, where the technology is already gaining remarkable attentions for the application. Particularly, leading industrialized nations are focusing on the PEM fuel dell with anticipation that this technology will find their place of applications in the vehicles and homes. In this study, demonstrate the multi physics modeling of a proton exchange membrane(PEM) fuel cell with interdigitated flow field design. The model uses current balances, mass balance(Maxwell-Stefan diffusion for reactant, water and nitrogen gas) and momentum balance(gas flow) to simulate the PEM fuel cell behavior.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.11
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• pp.2073-2082
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• 2010

The 4-th generation of mobile communication aims to realize global, fast and mobile communication service. The satellite communication charges a key role in this field. In this study, an OTM(On-The-Move) antenna which is mounted on ground vehicles and is used for mobile communication between vehicle and satellite was addressed. Since vehicles move during communication, active antenna line-of-sight stabilization is a core technology to guarantee high satellite communication quality. Stabilization of a satellite tracking antenna which consists of 2-DOF gimbals, an elevation gimbal over an azimuth gimbal, was considered in this study. Various disturbance torques such as static and dynamic mass imbalance torques, variation of moment of inertia according to elevation angle, friction torque related to vehicle motion, equivalent disturbance torque due to antenna roll motion, etc. were analyzed. As a robust stabilization control, rate feedback with sliding mode control and position feedback with proportional+integral control was suggested. To compensate antenna roll motion, a supplementary roll rate feed forward control was included beside of the feedback control loop. The feasibility of the analysis and the proposed control design were verified along with some simulation results.