• Journal of Institute of Control, Robotics and Systems
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• v.21 no.1
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• pp.1-6
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• 2015

This paper investigates the longitudinal flight dynamics and stability of flapping-wing micro air vehicles. Periodic external forces and moments due to the flapping motion characterize the dynamics of this system as NLTP (Non Linear Time Periodic). However, the averaging theorem can be applied to an NLTP system to obtain an NLTI (Non Linear Time Invariant) system which allows us to use a standard eigen value analysis to assess the stability of the system with linearization around a reference point. In this paper, we investigate the dynamics and stability of a hawkmoth-scale flapping-wing air vehicle by establishing an LTI (Linear Time Invariant) system model around a hovering condition. Also, a direct time integration of full nonlinear equations of motion of the flapping-wing micro air vehicle is conducted to see how the longitudinal flight dynamics appear in the time domain beyond the reference point, i.e. hovering condition. In the study, the flapping-wing air vehicle exhibited three distinct dynamic modes of motion in the longitudinal plane of motion: two stable subsidence modes and one unstable oscillatory mode. The unstable oscillatory mode is found to be a combination of a pitching velocity state and a forward/backward velocity state.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.326-331
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• 2006

The durability of recent motors is longer than the past one because there are the rapid technique development of the automobile industry and the vehicle maintenance of users. And then the importance of the durability test due to vibration is increased from day to day. So full vehicle and parts companies accomplish the durability test using various methods. The most public test method among them is the reliable field test but it bring on higher cost and period of the development process. The durability test using MAST(multi axis simulation table) is a solution in order to improve the development process of automobiles. Generally its excitation source uses the optimized road profiles that are obtained by the road test of belgian road, country road, cobbleston road and so on instead of a real field but the interrelations and influences accordingly vehicle damage are considered by a field test between specific roads and real fields in the first place. Therefore this study, in order to accomplish a basic research for the durability test using the MAST, performed on the real field driving test at various domestic roads and the results which are analyzed by PSD(power spectrum density) are compared with relative sensitivity among the roads. Consequently they can present a basic material for generation of road profiles which is applied to the durability test using MAST.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.3
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• pp.74-80
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• 2009

The objective of this paper was to investigate the slip rate and the slip frequency number of damper clutch of torque converter in 2.4L passenger vehicle with 5-speed A/T and analyze the effect of slip control and control strategy on driving characteristics and the fuel economy. The newly developed torque converter with the more durable wet friction material and the slip-controlled damper clutch system, the DCC system, was installed, which was easily compatible and amendable of the lock-up clutch of the base system. The vehicle has been tested on the fuel economy modes such as FTP-75, HWFET and NEDC (ECE15+EUDC) driving cycle at chassis dynamometer. The DCC mode (II), of which the control strategy had both the lock-up and the slip-controlled clutch, and the DCC mode (I) with full slip-controlled clutch were compared with the base system with only the lock-up clutch. As the research result, comparison to base system, the fuel consumption of the vehicle with the DCC control (II) was effectively improved by 6.6% and 7.7% on FTP-75 and NEDC mode.

• Journal of Institute of Control, Robotics and Systems
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• v.22 no.11
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• pp.912-918
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• 2016

This paper presents various strategies for humanoid vehicle driving and egress tasks. For driving, a tele-operating system that controls a robot based on a human operator's commands is built. In addition, an autonomous assistant module is developed for the operator. Normal position control can result in severe damage to robots when they egress from vehicles. To prevent this problem, another approach that mixes various joint control techniques is adopted in this study. Additionally, a footplate is newly designed and attached to the vehicle floor for the ground landing phase of the egress task. The attached plate enables the robot to step down onto the ground in a safe manner. For stable locomotion, a balance controller is designed for the humanoid. For the design of the controller, the robot is modeled using an inverted pendulum that consists of a spring and a damper. Then, a state feedback controller (with pole placement and a state observer) is built based on the simplified model. Many approaches that are presented in this paper were successfully applied to a full-sized humanoid, DRC-HUBO+, in the DARPA Robotics Challenge Finals, which were held in the United States in 2015.

• Transactions of the Korean hydrogen and new energy society
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• v.22 no.6
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• pp.859-867
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• 2011

The cold start problem is one of major obstacles to overcome for the commercialization of fuel cell vehicles. However, the cold start characteristics of fuel cell systems are very complicated since various phenomena, i.e. ice-blocking, electro-chemical reactions, heat transfer, and defrosting of BOP components, are involved in them. This paper presents a framework to approach the problem at a full stack scale using Axiomatic Design (AD). It was characterized in terms of Functional Requirements (FRs) and Design Parameters (DPs) while their relations were established in a design matrix. Considering the design matrix, the endplates should have low thermal conductivity and capacity without increase in weight or decrease in structural stiffness. Consequently, composite sandwich endplates were proposed and examined both through finite element analyses and experiments simulating cold start conditions. From the examinations, it was found that the composite sandwich endplates significantly contributed to improving the cold start characteristics of PEMFC.

• International Journal of Railway
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• v.2 no.3
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• pp.118-123
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• 2009

Railway track alignment Standards set a minimum lenght value for straight and circular alignments (art. 5.2.9.), in order to ensure passenger ride comfort in railway vehicles of which dynamic oscillations will thus have to be limited. The transitions between alignments can cause abrupt changes (usually called discontinuities or singular points of the alignment) of curvature, of rate of change of curvature or of rate of change of cant. A passenger is likely to experience effects due to the excitation of the elastic suspension of the vehicle which generates oscillations that are damped as the vehicle moves away from the singularity. The amplitude of these oscillations should be adequately attenuated by the damping of the suspension system within the interval between two successive singular points, especially to avoid resonances. Therefore minimum lengths between two successive singular points are stated in alignment standards. Nevertheless, these nonnative values can be overly conservative in some cases. As an alternative, track alignment designers could try to assess how much the excitation has been attenuated between two successive singular points and thus assess at which point a new singularity may be present without affecting ride comfort. Although such assessment can be made with commercial SW packages which simulate the dynamic behavior of a vehicle considered as a set of rigid bodies interconnected with elastic elements simulating the suspension systems (such as SIMPACK, ADAMS or VAMPIRE), a simplified and user-friendly computation method (based upon the analytical solution of differential equations governing the phenomenon) is made available in this paper to track design engineers, not always used to working with full dynamic models.

• Journal of Physiology & Pathology in Korean Medicine
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• v.20 no.4
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• pp.985-991
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• 2006

In the present study, the anti-inflammatory effect of Haepyoeiin-tang plus Antler water extract water extract was tested in Xylene-Application mouse ear acute inflammation model. The test articles were once dosed before Xylene-Application, and the changes on Dody weight and weights and histopathological observation of induced ear were conducted with ear histomorphometry, The increases of absolute and relative ear weight detected in vehicle control compared to that of sham, were significantly and dose-dependently inhibited by Haepyoejin-tang plus Antler in the present study, A classic acute inflammatory histological changes such as subcutaneous edema, hypertrophy and infiltration of inflammatory cells, was detected in vehicle control. However, these histological changes were significantly and dose-dependently inhibited by Haepyoeiin-tang plus Antler. In addition, the increases of ear thickness half and thickness full detected in the vehicle control, were also dose-dependently decreased in the all Haepyoeiin-tang plus Antler-dosing groups. Base on these results, it is concluded that Haepyoeiin-tang plus Antler water extracts have a clear anti-inflammatory effect on the acute inflammation. However, somewhat lower anti-inflammatory effects were detected in Haepyoeiin-tang plus Antler water extracts compare to that of Dethamethason and Dicrofenac. About 500 mg/kg of Haepyoeiin-tang plus Antler water extracts have similar effect compared to that of Dicrofenac 15 mg/kg.

• Journal of Physiology & Pathology in Korean Medicine
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• v.20 no.4
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• pp.875-881
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• 2006

In the present study, the anti-inflammatory effect of 'Jungcheonhwadamgangki -tang' water extract was tested in Xylene-Application mouse ear acute inflammation model. The test articles were once dosed before Xylene-Application, and the changes on body weight and ear weights and histopathological observation of induced ear were conducted with ear histomorphometry. The increases of absolute and relative ear weight detected in vehicle control compared to that of sham , were significantly and dose-dependently inhibited by Jungcheonhwadarn -gangki-tang in the present study. A classic acute inflammatory histological changes such as subcutaneous edema, hypertrophy and infiltration of inflammatory cells, was detected in vehicle control. However, these histological changes were significantly and dose-dependently inhibited by Jungcheonhwadam-gangki-tang. In addition, the increases of ear thickness half and thickness full detected in the vehicle control, were also dose-dependently decreased in the all Jungcheonhwadamgangki-tang-dosing groups. Base on these results, it is concluded that Jungcheonhwadamgangki-tang water extracts have clear anti-inflammatory effect on the acute inflammation, and about 500 mg/kg of Jungcheonhwadamgangki-tang water extracts have similar effect compared to that of Dicrofenac 15 mg/kg.

• Journal of Institute of Convergence Technology
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• v.2 no.1
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• pp.24-30
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• 2012

In this study, the trucks(2.9-liter) have been developed to use DME as fuel, and performance test of the vehicle's DME engine, power, emissions, fuel economy and vehicle aspects was conducted. For experiments, the fuel system(common-rail injectors and high-pressure pump included) and the engine control logic was developed, and ECU mapping was performed. As a result, the rail pressure from 40MPa to approximately 65% increase compared to the base injector has been confirmed that. Also, the pump discharge flow is 15.5 kg/h when the fuel rail pressure is 400rpm(40 MPa), and the pump discharge flow is 92.1 kg/h when the fuel rail pressure is 2,000rpm(40MPa). The maximum value of full-load torque capability is 25.5kgfm(based on 2,000rpm), and more than 90% compared to the level of the diesel engine were obtained. The DME vehicle was developed in this study, 120 km/h can drive to the stable, and calculated in accordance with the carbon-balance method of fuel consumptions is 5.7 km/L.

• Journal of Aerospace System Engineering
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• v.13 no.3
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• pp.64-69
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• 2019

The purpose of this study is to explore the current status and challenges of the space development system in Korea following the successful launch of test vehicle, the Korean space launch vehicle II on the 30th anniversary of space development and seek an alternative to the government organizations for efficient space development future. The study investigates the space development system of leading countries such as USA, France, and Japan with keen focus on the administrative organizations and thereafter draw implications for Korea. The analysis of the existing situation in Korea focuses on governance, such as space-related government organizations, space development agency, and specialized research funding agency. As a result, this study proposes the need for full-scale discussion on building a space agency.