• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.1723-1728
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• 2005

This article describes the fuzzy control of the 3-dimensional motion of the container cranes used in dockside container terminals. The container is suspended by four flexible cables via spreader, and due to the disturbances such as the wind and acceleration of cranes, the container undergoes translational(sway) and rotational position errors. And due to the uncertainty of weight and rotational inertia, accurate position control of container crane is difficult to realize. This paper, based on the analysis of 3-dimensional dynamics of container moving systems, describes the design of the fuzzy controller, which does not require the computation time to optimize the distribution of cable tension. The developed controller is shown effective in controlling the container position in the presence of gust and parameter uncertainties.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.6 s.111
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• pp.634-642
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• 2006

For the analysis of dynamic contact between a catenary and a pantograph of high-speed electrical train, the numerical solution of the equations of motion of the vehicle pantograph and the catenary system subjected to the contact condition is obtained. The whole equations of motion of the catenary and the pantograph are simultaneously time integrated with the strict application of the contact condition. For the stability of the numerical solution, with the cubic spline interpolation of the catenary displacement, the velocity and acceleration constraints as well as the displacement constraint are imposed on the contact point. Especially it is shown that the Coriolis and centripetal accelerations are critical for the accuracy and stability of the computation.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.6
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• pp.129-135
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• 2016

There have been many types of development and commercialization efforts for superconducting power applications with the continuous development of High Temperature Superconducting (HTS) conductors. In particular, HTS power cables are going to be commercialized in real power grids. A cryogenic refrigeration system should be used to keep it below 77 K, and its required cooling capacity continuously increases as the unit length of the HTS power cable increases. Among the many kinds of cryogenic refrigerator, a reverse Brayton refrigerator that uses turbo expanders is a promising refrigerator due to its efficiency and reliability. Among the various components in refrigerators, the cryogenic turbo-expander is the most important part for increasing efficiency and assuring reliability. The design of a 300 W class turbo-expander is described in this paper prior to the development of a 10 kW class turbo expander, which is the required capability for the commercialization of a HTS power cable. The impeller shape and rotation speed are determined based on the cycle analysis. The Eigen frequency and harmonic analysis are conducted with gas bearings at cryogenic temperatures to determine the operational stability.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2009.10a
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• pp.40-41
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• 2009

In general, ships are towed to keep the safe operations in harbor or channel by tug boats. Due to increase in ocean traffic, many accidents are happened in harbor or channel in these days. Therefore it is necessary to predict manoeuvrability of tug-barge system, and to assure the safety of that system. Turg-barge system is composed of tug boat, barge, and towing cable, connecting both ships. Manoeuvring equations of tug-barge system are suggested, and the scopes of model tests are discussed to establish the mathematical models for tug boats in this paper.

• Geomechanics and Engineering
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• v.27 no.6
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• pp.537-550
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• 2021

There are various technical problems need to be solved in the construction process of pre-setting an isolation wall into a double lane in the outburst prone mine. This study presents a methodology that pre-setting an isolation wall into a double lane without a coal pillar. This requires the excavation of two small section roadways to dig a wide section roadway, followed by construction of the separation wall. During this process the connecting lane is reserved. In order to ensure the stability of the separation wall, the required bearing capacity of the isolation wall is 4.66 MN/m and the deformation of the isolation wall is approximately 25 cm. To reduce the difficulty of implementing support the roadway is driven by 5 m/d. After the construction of the separation wall, the left side coal wall is brushed 1.5 m to make the width of the gas roadway reach 2.5 m and the roadway support utilizes anchor rod, ladder beam, anchor cable beam and net configuration. During construction, the concrete pump and removable self-propelled hydraulic wall mold are used to pump and pour the concrete of the isolation wall. In the process of mining, the stress distribution of coal body and isolation wall is detected and measured on site. The results demonstrate that the deformation of the surrounding rock of roadway and separation of roof in the roadway is small. The stress of the bolt and anchor cable is within equipment tolerance validating their selection. The roadway is well supported and the intended goal is achieved. The methodology can be used for reference for similar mine gas control.

• The Journal of the Korea Contents Association
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• v.10 no.5
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• pp.229-240
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• 2010

Most of all researchs and analyses in the field of television industry of Korea were related to Cable Television SO(System Operator), but few about PP(Program Provider) from the viewpoint of Industrial Theory in Korea. However, there wasn't a comprehensive research analysis in terms of the co-relationship of the market structure, market conduct and market performance of PP. This research analyzes co-relationship and dynamics of the market structure of PP, its market conduct and market performance in a comprehensive way in Cable TV industry. Especially this paper focuses on the analysis of 1)relationship and its influence between market structure and market conduct, 2) relationship and its influence between their market conducts and market performances and 3) relationship and its influence between market structure and market performance among 40 commercial PPs in terms of the theory of Industrial Organization in Korea. This paper is delated and reported as follows in conclusion : 1)the type of horizontal integration has an effect on the price and scale in the relationship between the structure and its conduct. 2)the price has effect on the revenue and viewing rate between the conduct and performance. And high dependency of the Cable TV license fee has an effect on viewing rate and revenue per subscribers(ARPU) between the conduct and performance. 3)The horizontal integration between the structure and performance had a positive effect on viewing rate and its product differentiation has an effect on the revenue per subscribers. Net cost of the product had a negative effect on the rate of profit.

• Wind and Structures
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• v.22 no.2
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• pp.211-234
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• 2016

Super long-span bridges provide people with great convenience, but they also bring traffic safety problems caused by strong wind owing to their high decks. In this paper, the large eddy simulation together with dynamic mesh technology in computational fluid dynamics (CFD) is used to explore the mechanism of a moving vehicle's transient aerodynamic force in crosswind, the regularity and mechanism of the vehicle's aerodynamic forces when it passes through a bridge tower's wake zone in crosswind. By comparing the calculated results and those from wind tunnel tests, the reliability of the methods used in the paper is verified on a moving vehicle's aerodynamic forces in a bridge tower's wake region. A vehicle's aerodynamic force coefficient decreases sharply when it enters into the wake region, and reaches its minimum on the leeward of the bridge tower where exists a backflow region. When a vehicle moves on the outermost lane on the windward direction and just passes through the backflow region, it will suffer from negative lateral aerodynamic force and yaw moment in the bridge tower's wake zone. And the vehicle's passing ruins the original vortex structure there, resulting in that the lateral wind on the right side of the bridge tower does not change its direction but directly impact on the vehicle's windward. So when the vehicle leaves from the backflow region, it will suffer stronger aerodynamic than that borne by the vehicle when it just enters into the region. Other cases of vehicle moving on different lane and different directions were also discussed thoroughly. The results show that the vehicle's pneumatic safety performance is evidently better than that of a vehicle on the outermost lane on the windward.

• Journal of Biosystems Engineering
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• v.29 no.5 s.106
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• pp.395-406
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• 2004

Most of tractors in the world have manual gear transmission, and some of small tractors have hydrostatic trans-mission(HST). Since the HST is expensive and has low power efficiency, it is being used for only small garden tractors. The continuously variable transmission(CVT) is an alternative to the HST or power-shift gear transmissions. The driver of the CVT tractor doesn't have to operate a shift lever since the CVT controller automatically controls the speed of tractor. Thus, it is much easier to operate the CVT tractor. For the easy and stable control of the CVT tractor, an appropriate control algorithm should be developed and the dynamic modeling should be carried out before making the prototype of CVT controller. This study was conducted to develop a simulation model of the CVT control system needed to develop a PID control algorithm. The simulation model consisted of variator dynamics, hydraulic system and control computer. And the simulation model was verified by experiment. The results obtained in this study can be utilized in the design of CVT tractors for practical use, but a lot of field tests and improvement of softwares would be necessary.

• Structural Engineering and Mechanics
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• v.61 no.6
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• pp.785-794
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• 2017

This paper is concerned with the comparative numerical and experimental study on the natural behavior and the motion responses of a 1/75 moored scale model of a 2.5 MW spar-type floating offshore wind turbine subject to 1-D regular wave. Heave, pitch and surge motions and the mooring tensions are investigated and compared by numerical and experimental methods. The upper part of wind turbine which is composed of three rotor blades, hub and nacelle is modeled as a lumped mass and three mooring lines are pre-tensioned by means of linear springs. The numerical simulations are carried out by a coupled FEM-cable dynamics code, while the experiments are performed in a wave tank equipped with the specially-designed vision and data acquisition system. Using the both methods, the natural behavior and the motion responses in RAOs are compared and parametrically investigated to the fairlead position, the spring constant and the location of mass center of platform. It is confirmed, from the comparison, that both methods show a good agreement for all the test cases. And, it is observed that the mooring tension is influenced by all three parameters but the platform motion is dominated by the location of mass center. In addition, from the sensitivity analysis of RAOs, the coupling characteristic of platform motions and the sensitivities to the mooring parameters are investigated.

• Wind and Structures
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• v.11 no.3
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• pp.179-192
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• 2008

In a wind tunnel experiment employing a reduced scale model, Reynolds number (Re) can hardly be respected. Its effects on the aerodynamics of closed-box bridge decks have been the subject of research in recent years. Stonecutters Bridge in Hong Kong is a cable-stayed bridge having an unprecedented central span of 1018m. The issue of Re sensitivity was raised early in the design phase of the deck of Stonecutters Bridge. The objective of this study is to summarise the results of various wind tunnel experiments in order to demonstrate the effect of Re on the steady state aerodynamic force coefficients. The results may provide an insight on the choice of scale for section model experiments in bridge design projects. Computational Fluid Dynamics (CFD) analysis of forces on bridge deck section was also carried out to see how CFD results are compared with experimental results.