• Journal of the Korean Society for Precision Engineering
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• v.28 no.6
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• pp.687-693
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• 2011

Spring-mass models have been widely accepted to explain the basic dynamics of human gait. Researchers found that the leg stiffness increased with gait speed to increase energy efficiency. However, the difference of leg stiffness change with gait speed between the young and the elderly has not been verified yet. In this study, we calculated the lower limb stiffness of the elderly using walking model with an axial spring. Vertical stiffness was defined as the ratio of the vertical force change to the vertical displacement change. Seven young and eight elderly subjects participated to the test. The subjects walked on a 12 meter long, 1 meter wide walkway at four different gait speeds, ranging from their self-selected speed to maximum speed randomly. Kinetic and kinematic data were collected using three force plates and motion capture cameras, respectively. The vertical stiffness of the two groups increased as a function of walking speed. Maximum walking speed of the elderly was slower than that of the young, yet the walking speed correlated well with the optimal stiffness that maximizes propulsion energy in both groups. The results may imply that human may use apparent limb stiffness to optimize energy based on spring-like leg mechanics.

• Journal of Power System Engineering
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• v.13 no.5
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• pp.18-24
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• 2009

This paper shows the result of development about the revolution system of azimuth thruster which of power is less than 250kW for small ship. Advanced Azimuth revolution system can revolve propeller and rudder from 360 degree so that this system for vessel maneuvering can be excellent of propulsion effectively. Fluid power control system for azimuth thruster is designed with PID control system by using CEMTool/SIMTool program. And the actuator used for servo valve can control rudder angle, pressure and direction. The first, We had a test for the angle control of revolution system. The result of angle control confirmed that it has the good efficiency from experiment result of time input degree $30^{\circ}$, $90^{\circ}$ and $180^{\circ}$. The second, We had to a test for the pressure characteristic of hydraulic motor. As a result, We confirmed the maximum pressure 3.5MPa and steady state 0.7MPa nom experiment result of time input degree $30^{\circ}$. In this paper, it is identified the pressure characteristic of hydraulic motor and angle control for azimuth thruster by AMESim, and it has been confirmed the usefulness of AMEsim modeling was verified by comparison between AMESim simulation results and experiments results.

• Journal of the Economic Geographical Society of Korea
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• v.16 no.3
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• pp.528-542
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• 2013

This paper attempts to explain the energy policy to respond to climate change that is debated in recent years. Especially by the case of Germany among the developed countries, the study investigates the direction, strategy and measure of energy policy which are implemented at the national level. The Energy policy of Germany revealed through this study will provide implications for the establishment and propulsion of the energy policy trying to overcome the crisis of energy resources and reduce greenhouse gas emissions in Korea. Firstly, this study reviews the major goal of German government's recent energy policy, and secondly discusses the various strategies and means of policy to achieve the main directions of Germany's energy policy.

• Aerospace Engineering and Technology
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• v.12 no.2
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• pp.193-201
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• 2013

Propeller is an important component of Human Powered Aircraft (HPA) propulsion system. HPA uses large diameter low rotational speed propeller to get high propeller efficiency. The propeller was designed by HPA propeller designing program. The propeller pitch is adjustable by rotating the blade axis angle at ground. Performance of the propeller for various parameters are analysed by the same program used for design. Off-design condition performance was also checked including pilot power change and flight speed change. The propeller was manufactured in ultra-light structure using carbon composite material down to 950g. The propeller was ground tested on ironbird and installed on KARI HPA. Finally the HPA flew 291m with this propeller.

• The KSFM Journal of Fluid Machinery
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• v.15 no.6
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• pp.11-17
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• 2012

The one way fluid structure interaction analysis on advanced propeller blade for next generation turboprop aircraft. HS1 airfoil series are selected as a advanced propeller blade airfoil. Adkins method is used for aerodynamic design and performance analysis with respect to the design point. Adkins method is based on the vortex-blade element theory which design the propeller to satisfy the condition for minimum energy loss. propeller geometry is generated by varying chord length and pitch angle at design point. Blade sweep is designed based on the design mach number and target propulsion efficiency. The aerodynamic characteristics of the designed Advanced propeller were verified by CFD(Computational Fluid Dynamic) and showed the enhanced performance than the conventional propeller. The skin-foam sandwich structural type is adopted for blade. The high stiffness, strength carbon/epoxy composite material is used for the skin and PMI(Polymethacrylimide) is used for the foam. Aerodynamic load is calculated by computational fluid dynamics. Linear static stress analysis is performed by finite element analysis code MSC.NASTRAN in order to investigate the structural safety. The result of structural analysis showed that the design has sufficient structural safety. It was concluded that structural safety assessment should incorporate the off-design points.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.24 no.6
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• pp.653-659
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• 2015

The aim of this study is to develop a technique for the accelerated life test of the capacitor in a propulsion control device of a traction inverter used for a high-speed train. Using this technique, the accelerated life test can possibly estimate the life cycle of a capacitor under various temperature conditions and irregularly applied voltage. The accelerated life test is conducted for the capacitor of the traction inverter. The common proceedings of this test are selection of failure mechanism, determination of accelerated stress, range determination of the accelerated stress, determination of the test condition, and distribution and determination of the sample. From this result, the continuous applied voltage was not considered for the acceleration factors anymore. Therefore, the final result having an acceleration factor of 9.4 (= 13,626/1,445) was observed. Furthermore, the life-shortening acceleration effect for the irregular applied voltage condition can be applied to various situations.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.21 no.1
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• pp.62-67
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• 2013

Human Powered Aircraft (HPA) should be light in weight and have high efficiency because power source of propulsion is human muscles. Airframe structure takes up most of empty weight of aircraft, so weight reduction of structure is very important issue for HPA. In this paper, design/analysis/test procedures for ultra light weight structure of the HPA developed by Korea Aerospace Research Institute (KARI) are explained briefly. Structural design is conducted through case studies on HPA in the USA and Japan. Loads analysis is performed to calculate design loads which is needed for structural design and analysis. Structural analysis is conducted for structure sizing. Static strength test of main wing spar which is primary structure of wing is performed to verify structural integrity.

• Journal of the Society of Disaster Information
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• v.4 no.2
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• pp.138-154
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• 2008

The conventional non-dig underground structure building method which made an appearance to reduce the social and environmental costs and maximize the efficiency of the social overhead capital facilities could not help being uneconomical because of many problems such as unnecessary excessive excavation, water leakage, obstacle interference, difficulty of curvilinear application and connection complexity between propelled and injected bodies due to indiscriminate application of small and large circular steel pipes without consideration of the site conditions. The T.S.T.M, in which a protruded square tube is applied as a propulsion and injection body in a design that considered site conditions such as ground condition, depth of soil and live load, was able to be economical as it solved the problems of water resistance, minimization of obstacle interference and curvilinearity, and we can see that it can be applied to all grounds by utilizing or complementing the target ground in terms of engineering. Also in configuring the transverse section, it is possible to not only secure excellent structural safety but also implement all of the above engineering characteristics not only in the square cross section but also in the arch cross section, so it was possible to build structures on any section or ground, and we could confirm the LCC reduction effect and the VE effect.

• Journal of the Society of Naval Architects of Korea
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• v.52 no.1
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• pp.34-42
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• 2015

The development of an azimuth thruster which has the function of dynamic positioning and propulsion has been greatly required as the demand of vehicles with it increases. To develop or design a reliable azimuth thruster, it is appropriate that the performance and cavitation observation tests should be conducted in the regime of high Reynolds number. In the present study, to satisfy high Reynolds number condition new dynamometer for a large azimuth thruster is manufactured and arranged in the test section of the Large Cavitation Tunnel (LCT). The test method composed of the open water and the cavitation observation tests is established successfully in LCT, considering the thruster design.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.975-979
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• 2008

Since tram has the advantages to reduce construction cost of infrastructure, to improve accessibility of passengers, and to offer visual pleasures, nowadays, it is one of light rails attracting public attention. Tram can be classified into two groups, one is a conventional steel-wheeled type, and the other is a rubber-tired type (bi-modal tram). The bi-modal tram propelled by the serial CNG hybrid propulsion unit has been developing since 2003 in Korea, which can realize both scheduled operation of railway and route flexibility of bus. Because the bimodal will be operated on both railway mode and bus mode, however, specific criteria and regulations for its design, certification, construction, operation and maintenance have not been determined definitely yet. In consideration of mobility enhancement for the old and the handicapped, motor vehicle safety standard and urban transit (railway vehicle) safety standard, several design specifications were proposed for car body and interiors of the bimodal tram vehicle. The design specifications proposed in this paper can be expected to promote passengers' comfort and safety, operation efficiency of the bimodal tram.