• Journal of the Korean Society for Railway
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• v.15 no.6
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• pp.531-536
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• 2012

This study presents a result on aero-acoustic characteristics of pantograph panheads. To analyze the fluid flow around the panhead and resulting sound radiation, simple models of panhead were used in the numerical simulations called Lattice-Boltzmann method. The simulation results were verified using the wind tunnel test. The main aerodynamic noise was generated from the vortex shedding which is characterized by the Strouhal number, flow speed and geometry. The reduction in the radiated noise with simultaneously achieving increased lifting force was implemented for the simple rectangular geometry used in this study. Also, it was shown that the radiated sound power was significantly reduced by minimizing vortex shedding using through-holes or streamline shapes.

• Korean Journal of Applied Biomechanics
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• v.12 no.1
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• pp.173-191
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• 2002

The purpose of this study was defined efficient throw motion pattern to obtain the quantitative data and to achieve successful bowling through kinetic - kinematic variables on the throw motion. Subject of group composed of three groups : Higher bowlers who are two representative bowlers with 200 average points and one pro-bowler. Middle bowlers who are three common persons with 170 average points. Lower bowler who are three common persons with 150 average points. Motion analysis on throw motion in three groups respectively has been made through three-dimension cinematography using DLT method. Two high-speed video camera at operating 180 frame per secondary. One-way ANOVA has been used to define variable relations. Analyzed result and conclusion are the following : The displacement of back of the hand must have wider difference of each right-left displacement to increase the spin of the ball. In high bowlers group, difference between the front-rear position of back of the hand in case of success and that in case of failure in follow throw is 0.17m. That is to say, momentum in case of success come to increase greatly, compared with that in case of failure. To increase the spin of the ball, the potential difference should be narrower in follow through. In case of the high bowlers, the velocity of the front-rear direction of the back of the hand has been the fastest both in release and follow through, compared with those in other groups, which has contributed to increasing the spin force of the ball. The orders in the resultant velocity of the back of the hand has shown the this : the finger tip$\rightarrow$the back of the hand$\rightarrow$wrist.These orders made the proximal segment support the distal segment. The distal segment has provided the condition to accelerate the velocity. In case of failure, the suddenly increased velocity has caused the failure in the follow through. Acutely flexing the angle of the back of the hand has contributed to lifting to increase the spin of the ball.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.10
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• pp.3658-3665
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• 2010

As the population of elderly people and disabled people are increased, various demands for human welfare using robot system are raised. Especially autonomous rehabilitation system using robot could reduce the human effort while maintaining the its intrinsic efficacy. This study deals with mobile gait rehabilitation system which combined with BWS (Body Weight Support) for training of elderly and handicapped people who suffer the muscle force weakness of lower extremity. BWS which is designed by kinematic analysis of body lifting characteristics and walking guide system are integrated with main control system and wheeled platform. This mobile platform is operated by UCS (User Command System) and autonomous trajectory planning algorithm. Finally, through the EMG (Electromyography) signal measuring and its analysis for subject, performance and feasibility of developed system is verified.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.25 no.5
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• pp.338-344
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• 2016

Recent trends in transport system for carrying heavy freight are that demands of a high efficiency, economic efficiency, convenience and safety are increased. Conventional transport systems were poor in transport efficiency and economic efficiency. And Safety problems can be caused to products and workers. In order to overcome these problems, an air cushion transport device with a high-pressure air is required. The air cushion transporter is a device for reducing the frictional force of floor surface and lifting the heavy freight by spraying the high-pressure air to the floor. Technology to float and transfer freight using high-pressure air is very convenient and initial cost can be reduced. In this paper, the study on the levitation performance and transport efficiency of air cushion transport system is conducted and verified that air cushion transporter has a significantly higher transport efficiency than conventional heavy handling systems.

• Journal of Power System Engineering
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• v.16 no.5
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• pp.40-46
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• 2012

For free surface flow problem, a high-order spectral/boundary element method is adapted as an efficient numerical tool. This method is one of the most efficient numerical methods by which the nonlinear gravity waves can be simulated and hydrodynamic forces also can be calculated in time domain. In this method, the velocity potential is expressed as the sum of surface potential and body potential. Then, surface potential is solved by using the high-order spectral method and body potential is solved by using the high-order boundary element method. Using the combination of these two methods, the free surface flow problems of a submerged moving body are solved in time domain. In the present study, lifting surface theory is added to the former work to include effects of lift force. Therefore, a new formulation for the basic mathematical theory is introduced to contain the lift body in calculation.

• Journal of the Society of Naval Architects of Korea
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• v.48 no.2
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• pp.147-157
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• 2011

A RANS(Reynolds averaged Navier-Stokes) based numerical method is developed for the evaluation of ship resistance and self-propulsion performances. In the usability aspect of CFD for the hull form design, the field grid around practical hull forms is generated by solving a grid Poisson equation based on the hull surface grid generated from station offsets and centerline profile. A body force technique is introduced to model the effects of the propeller in which the propeller loads are obtained from potential flow analysis using an unsteady lifting surface method. The free surface is captured by using a two-phase level-set method and the realizable $k-{\varepsilon}$ model is used for turbulence closure. The hull attitude in vertical plane, i.e., trim and sinkage, is calculated by using a quasi-steady method and then considered in the computation by translating and rotating the grid system according to the values. For the validation of the proposed method, the numerical results of resistance tests for KCS, KLNG, and KVLCC1 and of self-propulsion test for KCS are compared with experimental data.

• Journal of the Ergonomics Society of Korea
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• v.34 no.1
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• pp.1-10
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• 2015

Objective: The purpose of this paper is to evaluate old and newly designed ammunition boxes from an ergonomic point of view. Background: The ammunition boxes made of wood, which are currently used by the military, have some difficulties such as corrosion and damage of ammunition, environmental pollution, and stock management. Also, damages to the wooden ammunition boxes take place frequently, because soldiers carry them manually. Method: Sixteen participants volunteered to randomly perform lifting, carrying, and side-by-side moving tasks with 4 different old and new boxes, respectively for the ammunitions of 5.56mm, 60mm, 81mm, and 105mm in diameter. The old boxes are made of wood and are currently used in the military, while the new boxes are made of plastics. The joint moments of the elbow, shoulder, back, and knee were measured by using a motion analysis system and force platforms. In addition, an electromyographic system was used to measure the forces of hand and wrist muscles. Results: In most tasks, new boxes caused less joint moments at the elbow and shoulder than old boxes, because the new boxes were lighter and smaller than the old boxes. New boxes also derived less hand and wrist muscle forces due to the provision of fixed hard handles rather than string handles. Conclusion: The ergonomically designed new boxes could reduce the physical stresses of soldiers manually handling ammunitions and be helpful for storage and reuse. Application: This study shows an ergonomic application example for product development and evaluation.

• Journal of Navigation and Port Research
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• v.30 no.5 s.111
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• pp.375-379
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• 2006

The keel attached on bottom of hull part prevents yacht from flowing sideway by sailing posture. The keel remove a heel moment and make the force of stability. The selection of suitable keel is important bemuse it has an influence on the safety. Also the appendage attached on bottom of keel part lower ballast weight center and have influence on hull stability. The optimum shape about the keel is very important. So this study has compared with characteristics of resistance depending on the shape of the lower part of fin keel in the same surface of water submersion, we have attached three different types of models of lower part of fin keels to the model ships using circulating water channel and analyzed resistance characteristics per shape to arrive at the optimum shape of reduction of resistance.

• Journal of the Society of Naval Architects of Korea
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• v.59 no.1
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• pp.1-8
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• 2022

To understand physical phenomena of ship maneuvering deeply, a numerical study based on computational fluid dynamics is required. A computational method that can simulate the interaction between the ship hull, propeller, and rudder will provide informative local flows during ship maneuvering tests. The analysis of local flows can be applied to improve a physical model of ship maneuvering that has been widely used in maneuvering simulations. In this study, the numerical program named as WAVIS that has been developed for ship resistance and propulsion problems is extended to simulate ship maneuvering by free-running tests. The six degree-of-freedom of ship motion is implemented based on Euler angles and the overset technique is applied to treat the moving grid of ship hull and rudder. The propulsion force due to a propeller is calculated by a panel method that is based on the lifting-surface theory. The newly extended code is applied to simulate turning and zig-zag tests of KCS and the comparison with the available experimental data has been made.

• Journal of Practical Agriculture & Fisheries Research
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• v.10 no.1
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• pp.153-167
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• 2008

High temperature and natural sun light are considered as the core conditions for high quality and large quantity of Phellinus baumii production. However still now on there has been a mistake of excessively cutting off the natural light by spreading the closing nets on the mushroom cultivating house. For an example there are many houses where the closing nets under the roofs be extended to cover the sides of the houses, which way prevents the mushrooms in the houses from receiving sufficient natural sun light and getting the temperature sufficiently to grow so that the quantity and quality of the produced mushrooms are lowered even though the mushrooms can grow in those conditions. In order to avoid this mistake, the closing nets must be placed on the roofs of the houses only without dropping them to cover the sides. Further more when the closing nets are placed triply at the beginning stage of Phellinus baumii's growth in the house, the nets restrain the internal temperature of the house going up and intercept the natural bright light flowing into the house so that the growing tardiness occur to the Phellinus baumii. Therefore the roof only must have been covered by the closing net for 65% cutting off the light until May, and then covered by double folded the net for June, triple folded the net for July and August, double folded the net for September, and the single net for October. When the ventilation in the house has been maintained until the house tightly balloon out through controling lifting force of internal air, the Phellinus baumii can grow well while the bed logs themselves aren't dried out. Marketing is also very much important as well as increasing quality and quantity of Phellinus baumii production.