• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.658-663
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• 2000

Slopping phenomena deteriorate the productivity and the stability of operation in oxygen converter process. To predict and prevent that, it needs reliable perception of the internal state of the oxygen converter chamber. Equipment was developed to measure the dynamic and static behavior of the oxygen-blowing lance 3-dimensionally and the measured signal is analyzed in relation to slopping phenomena. It was found that the behavior of the lance is strongly correlated to the change of slag foam height and the instability of molten steel behavior. So slopping phenomena can be predicted by simultaneously analyzing the measured behavior of the lance and the control factors such as the flow rate of oxygen and the height of lance.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.53 no.3
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• pp.140-151
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• 2004

This paper presents the HVDC system modelling for analysis of subsynchronous oscillation and the design of the subsynchronous oscillation damping controller in HVDC system with the aid of novel eigenvalue analysis program. The HVDC system models include both the steady-state model for power flow calculation and the dynamic model for constructing the state matrix. The design procedures of the subsynchronous oscillation damping controller (SODC), which is integrated with PI controller at rectifier, consist of three steps:1) to identify the dominant torsional oscillation mode in the AC/DC system;2) to determine the parameters of the SODC for compensating the phase lagging due to the rectifier controller;3) to validate the control parameters and to determine the appropriate gain using a time-domain simulation program. The proposed design method has been tested against two AC/DC systems for validation.

• Tribology and Lubricants
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• v.18 no.1
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• pp.55-60
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• 2002

In many dynamic systems, there are unwanted oscillation which may arise the reduction of performance. Especially in low sliding speed condition, the stick-slip is an important issue because it because unstable motion as well as inaccurate position control in the system. Most previous works on the stick-slip are, however, only concerned with simple modeling under the condition of constant normal force. The normal force and the amount of hydraulic oil are variable with a cylinder stroke in the telescopic boom. This paper presents the pressure variations during stick-slip with the cylinder of telescope boom. Pressure variations by stick-slip has a similar pattern to that of single mass-spring model. The stick-slip is gradually decreased by means of increased flow rate.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1998.04a
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• pp.139-146
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• 1998

The prototype ASME III motor actuated Y-type globe valve has been tested to identify dynamic characteristics. The valve is Seismic Category I equipment and has the function to control water flow in the safety-related system. In this study, two different types of structural identification test i.e. swept sine and broadband random, have been performed at various levels of excitation to verify the effects of test method and excitation level on cross coupling effect as well as natural frequencies and damping values. It was found that swept sine test and broadband random test showed similar natural frequencies, and that the primary interaction was exhibited between horizontal and vertical axes.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.964-968
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• 2003

Hermetic rotary compressor is one of the most Important components for air conditioning system since it has a great effect on both the performance and the noise and vibration of He system. Noise and vibration of rotary compressor is occurred due to gas pulsation during compression process and unbalanced dynamic force. In order to reduce noise and vibration. it is necessary to identify sources of noise and vibration and effectively control then. Many approaches have been tried to identify noise sources of compressor. However, compressor noise source identification has proven to be difficult since the characteristics of compressor noise are complicated due to the interaction of the compressor parts and gas pulsation. In this work, Statistical Energy Analysis has been used to trace the energy flow in the compressor and identify transmission paths from the noise source to the sound field.

• The Journal of Society for e-Business Studies
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• v.4 no.1
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• pp.145-157
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• 1999

The challenge is to maximize the time-to-market benefits of concurrent engineering while maintaining control of data and distributing it automatically to the people who need it when they need it. The way PDM systems cope with this challenge is that master data is held only once in a secure vault where its integrity can be assured and all changes to it monitored, controlled and recorded. The structure of PDM is various from vendor, but they have common module. That is PDM and it is most important. The goal is to design the workflow in PDM using object-oriented modeling method. The past methods have concentrated on the flow between workflow engine and agent, but this paper will focus on task. We will model task as individual object. This paper uses OMT(Object Modeling Technique) by James Rumbaugh for base modeling tool and uses DCOM(Distributed Component Object Model) for base ORB(Object Request Broker). Research object is to design the static object model, to design state change by dynamic model and to design data transition by functional model.

• Proceedings of the Korea Information Processing Society Conference
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• 2002.11b
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• pp.1277-1280
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• 2002

화상회의 시스템들은 여러 명의 사람들에게 멀티미디어 데이터를 공유하여 전송하기 때문에 안정적인 대역폭을 보장받지 못하며, 계속적으로 변화하는 네트워크 상태에서 최적의 서비스를 제공하기 위해서는 동적 흐름제어 기법이 필요하게 된다. 동적 흐름제어 기법은 최적의 서비스를 제공하기 위해서 사용 대역폭이 클 경우에는 데이터의 량이 많은 고품질의 데이터를, 사용 가능한 대역폭이 낮을 경우에는 데이터의 량이 적은 저품질의 데이터를 생성한다. 본 논문에서는 기존의 두 가지 흐름제어 기법에서 사용된 측정 요소인 패킷 손실율과 왕복 시간외의 성능을 개선시킬 수 있는 요소인 네트워크 상태에 따른 제어 메시지의 빈도수와 데이터의 량을 이용한 동적 흐름제어 기법을 제안한다. 또한 실험을 통하여 기존의 동적 흐름제어 기법과 제안한 동적 흐름제어기법의 성능을 비교하였다.

• Journal of Industrial Technology
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• v.18
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• pp.323-328
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• 1998

A current controlled VSI-PWM rectifier and inverter with capacitor dc link is regarded as one of the most promising structures for three-phase to three-phase to three-phase power conversion. This type of converter normally requires twelve switches for a rectifier and inverter composed of self turn-off switch such as a bi-polar transistor or IGBT with an anti-parallel diode. In this paper, a new three-phase to three-phase converter for ac motor drives is proposed. The proposed converter employs only eight switches and has the capability of delivering sinusoidal input currents with unity power factor and bidirectional power flow. This paper describes the feasibility and the operational limitations of the proposed structure. A mathematical model of the system is derived using generalized modulation theory and experimental results for steady state and dynamic behavior are presented to verify the developed model.

• Proceedings of the Korean Information Science Society Conference
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• 2005.07a
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• pp.568-570
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• 2005

광대역 망에서 범용 TCP를 사용하는 경우 최대 전송 윈도우의 크기가 제한되어 가용한 망 자원이 낭비된다. 이를 해결하는 일반적인 방법은 윈도우 스케일 옵션을 사용하는 것인데 이 경우 송신측의 응용를 수정해야 하는 단점이 있다. 본 논문에서는 이를 해결하기 위하여 송신측을 수정하지 않고 전송 윈도우의 크기를 증가시키는 방법을 제안한다. 이 방법에서는 송수신측 사이에 있는 Snoop 게이트웨이가 망의 상태와 수신측의 처리 능력을 동적으로 파악하여 최적의 윈도우 확대 계수를 결정하고, 이 계수에 상응하는 수의 응답 패킷을 송신측에 전송하여 전송 윈도우 크기가 확대된 효과를 얻는다. 특히, 이 방법은 서로 다른 특성을 갖는 망이 snoop 게이트웨이를 사용하여 2-way 세그먼트 방식으로 연동된 환경에서 부가적인 비용없이 단대단 시맨틱을 유지하면서 성능을 향상시킬 수 있다.

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.1075-1077
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• 2003

본 논문에서는 직렬주입변압기가 없는 다중브리지 형태의 새로운 UPFC를 제안하고 그 특성을 분석한 내용에 대해 기술하고 있다. 송전계통에 적용 가능한 UPFC의 새로운 토폴로지를 제안하고 상세모델을 통하여 계통의 전력조류제어 및 파도상태시의 동특성을 시뮬레이션 한다. 1기무한모선 전력계통인 138kV 송전선로에 UPFC가 연결되어 있는 것으로 가정하여 제안하는 시스템의 동특성을 EMTDC 시뮬레이션으로 분석하였다. 제안하는 시스템은 직렬주입변압기가 없이 직접 선로에 연결하는 것이 가능하다. H-브리지 인버터의 수를 증가시킴으로써 동작전압을 유연하게 높일 수 있다.