• Proceedings of the KIEE Conference
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• 1999.11c
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• pp.506-508
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• 1999

In the distributed control systems where the control components, controllers and sensors are distributed on a communications network, there exist network time delays on communication lines between the system components. This paper deals with the ramp tracking controller design issue for such systems. Time delay terms are converted into the rational terms using Pade approximation method and the system is augmented with two integrators for ramp tracking. For this system, $\mu$-controller design method, which enables to meet not only performance requirements but robust stabilities simultaneously, is employed.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3068-3073
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• 2007

Aerodynamic forces and moments have been used to control rocket propelled vehicles. If control is required at very low speed, Those systems only provide a limited capability because aerodynamic control force is proportional to the air density and low dynamic pressure. But thrust vector control(TVC) can overcome the disadvantages. TVC is the method which generates the side force and roll moment by controlling exhausted gas directly in a rocket nozzle. TVC is classified by mechanical and fluid dynamic methods. Mechanical methods can change the flow direction by several objects installed in a rocket nozzle exhaust such as tapered ramp tabs and jet vane. Fluid dynamic methods control the flight direction with the injection of secondary gaseous flows into the rocket nozzle. The tapered ramp tabs of mechanical methods are used in this paper. They installed at the rear in the rocket nozzle could be freely moved along axial and radial direction on the mounting ring to provide the mass flow rate which is injected from the rocket nozzle. In this paper, the conceptual design and the performance study on the tapered ramp tabs of the thurst vector control has been carried out using the supersonic cold flow system and shadow graph. Numerical simulation was also performed to study flow characteristics and interactions between ramp tabs. This paper provides to analyze the location of normal shock wave and distribution of surface pressure on the region enclosed by the tapered ramp tabs.

• Journal of Digital Convergence
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• v.10 no.11
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• pp.59-65
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• 2012

The evolution of cloud computing service over the recent years is potentially one of the major advances in information and communication technology. However, if cloud computing service is to achieve its potential, there needs to be a clear understanding of the various issues such as service security, performance and availability and so on, both from the perspectives of the providers and the consumers of the cloud service. As more and more information on individuals, companies and public sectors are placed in the cloud service, concerns are beginning to grow about just how safe and reliable an environment it is. In order to overcome these situations, the Korea cloud service certification system and U.S. FedRAMP were performed in each country. This paper aims at comparing and analyzing between Korean cloud service certification systems and U.S. FedRAMP and describing the difference between them. Eventually, we propose the improvement strategy of Korea cloud service certification systems based on the comparison results between them.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.5D
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• pp.579-585
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• 2009

In spite of the proven effectiveness of ramp metering system, it has not been successfully implemented in Korean setting. The purpose of this paper is to select target locations to introduce ramp metering into the Korean expressway system. For this, domestic standards to introduce ramp metering have been presented after reviewing those of the US. The major criteria are level of service (LOS), the existence of detour route, space for queue build-up and opened ramp. 15 different locations were selected and AHP has been used to make priority among them. Intuitively, the result of priority was in accordance with the congestion and traffic volume. The core results identified in this paper is expected to be used in different cities and expressway networks elsewhere.

• International Journal of Automotive Technology
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• v.8 no.1
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• pp.59-66
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• 2007

High frequency excitation terms in a cam profile can excite vibration of a cam follower system. In this paper, modified smoothing spline curves are used to reduce the high frequency terms. The essential difference between the proposed method and other existing approaches is its ability to make the principal cam motions smooth while still exactly satisfying boundary conditions of follower displacement, velocity and acceleration. The boundary values usually depend on the ramp properties of a cam. Our method, thus, allows designers to smooth the existing cam motion without any damages on its ramp areas. Because the ramp height, velocity and acceleration are maintained exactly, more radical smoothing is possible. An example shows that the proposed method can be a powerful tool of cam profile smoothing, which removes high frequency components in the cam profile excitations without any changes in ramp properties.

• The Journal of Korean Physical Therapy
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• v.18 no.1
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• pp.95-106
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• 2006

Purpose: The aim of this study was to investigate the kinematics of young adults during ramp climbing at different inclinations. Methods: Twenty-three subjects ascended and descended four steps at four different inclinations(level, $8^{\circ},\;16^{\circ},\;24^{\circ}$). Temporal-spatial parameters were measured by GaitRite system(standard mat). Groups difference was analysed with on-way ANOVA and Student-Newman-Keuls test. Results: The different kinematics of ramp ascent and descent were analysed and compared to level walking patterns. In ascending ramps, step length and stride length decreased with $24^{\circ}$ inclination (p<.000). Stance duration increased with $24^{\circ}$, but swing duration decreased with $24^{\circ}$ inclination (p<.000). Step time and velocity decreased with $16^{\circ}C,\;24^{\circ}$ inclination (p<.000). Cadence decreased with all inclination($8^{\circ},\;16^{\circ},\;24^{\circ}$)(p<.000). In descending ramps, step length and stride length, velocity decreased with all inclination($8^{\circ},\;16^{\circ},\;-24^{\circ}$)(p<.000). Stance duration increased with all inclination($8^{\circ},\;-16^{\circ},\;-24^{\circ}$) and swing duration decreased with all inclination($-8^{\circ},\;-16^{\circ},\;-24^{\circ}$)(p<.000). But Step time was not differentiated with different inclinations. Cadence decreased with only. $8^{\circ}$ inclination(p<.05). Conclusion: These results suggest that there is a certain inclination angle or angular range where subjects do switch between level walking and ramp walking gait pattern. This shows their motor control strategy between level and ramp walking. Further studies are necessary to confirm and detect the ascent and descent ramp gait patterns.

• The KSFM Journal of Fluid Machinery
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• v.18 no.5
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• pp.49-53
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• 2015

Thrust vector control is the method which generates the side force and roll moment by controlling exhausted gas directly in a rocket nozzle. TVC is classified by mechanical and fluid dynamic methods. Mechanical methods can change the flow direction by several objects installed in a rocket nozzle exhaust such as tapered ramp tabs and jet vane. Fluid dynamic methods control the flight direction with the injection of secondary gaseous flows into the rocket nozzle. The tapered ramp tabs of mechanical methods are used in this paper. They installed at the rear in the rocket nozzle could be freely moved along axial and radial direction on the mounting ring to provide the mass flow rate which is injected from the rocket nozzle. TVC of the tapered ramp tabs has the potential to produce both large axial thrust and high lateral force. We have conducted the experimental research and flow analysis of ramp tabs to show the performance and the structural integrity of the TVC. The experiments are carried out with the supersonic cold flow system and the schlieren graph. This paper provides to analyze the location of normal shock wave and distribution of surface pressure on the region enclosed by the tapered ramp tabs.

• Journal of Korean Port Research
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• v.14 no.4
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• pp.419-427
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• 2000

Today travel demand continues to increase with spread of economic zones. Also, urban freeway plays an important role in intra-zone transportations as a major corridor in a big city. However, most of urban freeways experience a severe congestion with the excess of inflowing or outflowing traffic through freeway ramps. The purpose of this study is to identify the traffic characteristics, analyze the relationships between the traffic characteristics and finally construct the speed predictive models on the ramp junctions of urban freeway under the intelligent transportation system(ITS) settings. From the analyses of traffic characteristics following results were obtained: ⅰ) 24 hours average traffic characteristics flow, occupancy, speed under the ITS settings showed about 40%, 38%, 8.8% increase each on urban freeway junctions period when compared with that under the non-ITS settings each other. Free flow speed and traffic flow on the mainline sections of urban freeway under the ITS settings also showed about 20% and 17% increase when compared with that under the non-ITS, respectively. ⅱ) The upstream when compared speed( $S_{u}$)and downstream occupancy( $O_{d}$) were especially shown to have higher explanatory powers on the stable flow ramp junctions, but the upstream speed( $S_{u}$) and downstream flow( $V_{d}$) were especially shown on the unstable flow ramp junctions of urban freeway under the ITS settings.ngs.ngs.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.5
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• pp.533-536
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• 2014

In this paper, a near optimal decentralized observer-controller design method is proposed for ramp metering systems based on SDRE (State Dependent Riccati Equation) approach. The optimal nonlinear observer gain is parameterized in terms of the solution matrix of an SDRE. This paper gives a simple algorithm to compute the near optimal observer gain. The optimal control design problem is also considered. Finally, numerical simulation results are given to illuminate the effectiveness and practicality of the proposed design method.

• Korean Journal of Applied Biomechanics
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• v.18 no.4
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• pp.59-65
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• 2008

The purpose of this study was to investigate the shift of COP pathway and the plantar foot pressure among level walking and stairs and ramp climbing in young and elderly people. Plantar foot pressure was measured by MatScan system(Tekscan, USA). Statistical analysis was used One-way ANOVA to know the characteristics of peak plantar pressure during walking with different the facilities. In young adults, COP pathway during stairs climbing was slightly shorten and trended to abduct at forefoot. COP pathway during ramp climbing was also shorten but trend to adduct at forefoot. Peak plantar pressure of 2-3 metatarsal head and heel during ramp climbing was more decreased than level walking. In elderly people, COP pathway during stairs climbing was more shorten and abducted than leve walking and COP pathway during ramp climbing was more unstable than level walking. Peak plantar pressure of first metatarsal head increased at stair climbing and decreased at ramp climbing. That of second metatarsal head and heel was more decreased at ramp climbing. Conclusionally, Peak plantar pressures of each foot region generally increased and more changed during ramp climbing.