• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.775-779
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• 2001

In optical disk drive (ODD), disk rotation speed has been increasing rapidly to achieve high data transfer rate. High servo bandwidths for focusing and tracking actuator are required to follow dynamic disturbance by high rotation speed in ODD. However, the servo bandwidth is significantly limited by some vibration modes which are induced by the flexibility of moving part. In this work, the vibration modes affecting bandwidth of actuators are suppressed by modifying actuating force by VCM. For this, the relation between the horizontal component of the actuating force and vibration mode is analyzed and force characteristic affecting to vibration mode is obtained through electromagnetic and structural analysis using simulation program.

• Proceedings of the KIPE Conference
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• 2016.11a
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• pp.208-209
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• 2016

본 논문에서는 가동물체형 AFPM 파력 발전기용 시뮬레이터 구현 및 실험을 수행하였다. 파력 발전기는 파도의 에너지를 이용하여 부이의 움직임에 따라 발전하는 방식이다. 기존의 소형 파력 발전 시스템의 경우 단순히 전파 정류하여 축전지에 충전하는 방식을 사용한다. 그러나 전파 정류기를 사용하는 경우 파도에 속도에 따른 최적의 발전량을 제어하지 못해 발전 효율이 떨어지는 단점이 있지만, 인버터를 사용하는 경우 속도에 따른 발전량을 순시 적으로 제어할 수 있어 발전 효율을 높일 수 있다. AFPM 파력 발전기의 제어를 위하여 전류제어기와 센서리스 알고리즘을 구성하였으며 구현된 제어기는 파력 발전 시뮬레이터 실험을 통하여 회전자 위치 추정 및 속도에 따른 제어 성능을 확인하였다.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.5
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• pp.61-68
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• 2021

Movable weirs with multi-stage control are necessary in many Korean rivers to actively control the water storage level. A mesh dependency test was performed to determine the appropriate number of meshes for structural analysis of movable weirs. The standing angles of movable weirs were set to 60°, 45°, 30°, and 15° for stress analysis. The standing angle of 0° was excluded from the analysis because it was unloaded. Changes in the standing angle led to changes in the water depth, maximum pressure, maximum strain, and maximum stress. The maximum average stress and the structural safety of the multi-stage control movable weir were computed and tested using the Ansys FEA software package.

• Journal of Korean Tunnelling and Underground Space Association
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• v.6 no.2
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• pp.171-182
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• 2004

This study is focused on finding out the mechanical behavior of pillars and the ground adjacent to the tunnel depending on the central tunnel size and the invert during the construction of 2 arch tunnels in the sandy ground. Model tests were performed in the trap door system, which was composed of 3 separately movable plates. Central pillar was installed on the central movable plate to measure the pillar loads during the excavation of pilot tunnel and the main tunnel. The load-transfer and the loosening load were measured at the bottom plates adjacent to the 2 arch tunnels. The ground settlement and displacement of the tunnel lining were also measured. As results, not only pillar load but also the load transfer mechanism was influenced by the construction sequences, central tunnel size, and the invert.

• Fire Science and Engineering
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• v.27 no.5
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• pp.8-14
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• 2013

In the subway, various fires continue to take place across the world. In the Daegu subway accident in 2003, many people were damaged by shortened visibility range caused by toxic gas and smoke. This paper, assuming that a subway fire happens in the Mandeok Station of the subway system in Busan, analyzed different smoke-spreading situations depending on the ventilation situation at its platform (opening of the train doors, operation of ventilation facilities in the tunnel, and working of fire door), using FDS. The calculation proved that it would be more effective to secure evacuation route when the ventilation facilities of the tunnel are not operated, than when they are on. And, it was also found that the case where the doors of the platform to the escape route and only the platform-facing doors of the subway car on fire office are open would be more effective to ventilation than the case where all the doors are open. And, it was found to be important that the fire doors of the platform are working properly.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.3A
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• pp.277-286
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• 2010

Derrick or caterpillar crane is generally used for the long-span/cable-stayed bridge construction by pre-cast segment lifting from over-land or water transportation. The heavy weight of them, however, could make defects on unstable under-construction structure and, furthermore a method of conventional segment transportation is also able to occur additional time and cost. In this study, in order to improve conventional construction method, the newly developed derrick crane is mainly considered. It could be not only eccentrically loadable on constructing girder but having rotatable boom for segment transportation from back-side. A series of construction stage using developed derrick crane is defined and also its numerical analysis is conducted. To reflect load characteristics of developed derrick crane on construction stage analysis, on/out of service load is separately calculated by considering vertical/lateral rotation range of boom and it is loaded on 4 fixed positions of crane. The derrick crane on this study could be time and cost saving solution for cable-stayed bridge construction and also make contributions to construction load reduction in its process.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1994.11a
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• pp.51-58
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• 1994

가스터빈 발전은 연료를 연소하여 연소가스로 직접 터빈을 회전시켜 터빈에 연결된 발전기에 의해 발전하는 방식으로 연료로는 중유, 원유, 경유, 가스등을 사용한다. 주요설비는 공기압축기, 연소기, 터빈 및 발전기로 구성되며 이중 고온부는 연소기와 터빈이다. 가스터빈의 효율은 터빈입구온도(TIT : TBN INLET TEMP)에 의존하는데 현재까지 약 1,30$0^{\circ}C$ 급의 가스터빈이 운전중이며 앞으로 1,50$0^{\circ}C$ 급의 고효율 가스터빈에 도전하고 있으며 연소가스의 고온화는 고온부의 재료개발, 냉각기술, 코팅기법의 향상과 더불어 이루어질 수 있다. 가스터빈의 고온부 부품인 연소기, 터빈의 동익(Moving blade) 및 정익(Fixed blade) 재료로 초내열합금이 계속 개발중이며 또한 각 부품에 대한 공기냉각기술, 코팅재료 및 기법도 개발중이다. 그러나 현재 국내에서 가동중인 가스터빈은 빈번한 기동정지로 열 사이클에 의한 부품의 손상이 심각한 실정이므로 고효율 가스터빈 개발과 이에 대한 정비기술 개발이 병행하여야만 안정된 전기공급을 이룰 수 있다는 차원에서 가스터빈은 고온부품의 정비기술에 대한 그 현황과 전망에 대해 살펴보고자 한다.

• Fire Science and Engineering
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• v.20 no.4 s.64
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• pp.98-104
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• 2006

The Fire Protection Regulatory documents require the fire-resistive rating of fire barrier penetration seals be same as that of fire barriers. Pilot application of penetration seal evaluation for K nuclear plant, built before penetration seal requirements were made, was done. In this evaluation, visual inspection and estimating fire rating by comparing installed configuration with tested configuration of penetration seals, called bounding approach method, were applied. Further improvements for retrofit and maintenance are recommended with penetration seal evaluation results also. The practical use of the methodology adopted in this study and the evaluation result of K nuclear plant will be anticipated for other plant's penetration seal evaluation.

• Journal of the Korean Society for Marine Environment & Energy
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• v.6 no.4
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• pp.37-44
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• 2003

In order to evaluate the contribution of MMSTP operation to the improvement of marine water quality of Mokpo harbour and to estimate the change of pollution loads flowing into Mokpo harbour after the operation of Mokpo Municipal Sewage Treatment Plant (MMSTP), the pollution loads flowing into Mokpo harbour from land in dry weather were surveyed and estimated on the bases of the seasonal flow rates and the seasonal water qualities of streams and effluents located around Mokpo harbour from summer, 1997 to spring, 1998 before the operation of MMSTP, and the pollution loads of the inflow and the effluent of MMSTP were also surveyed and estimated from winter, 1998 to spring, 1999 after the operation of MMSTP. The treatment rates of MMSTP were shown to be about 49% in COD, 76% in TSS, 79% in VSS, 3% in T-N, 7% in DIP, 29% In T-P and -32% in DIN. The change rates of pollution loads flowing into the inner harbour of Mokpo due to the operation of MMSTP were shown to be about 56% in COD, 78% in TSS, 84% in VSS, 45% in DIN, 22% in T-N, 34% in T-P and -14% in DIP The contribution rates of MMSTP operation to the reduction of total pollution loads flowing into the entire Mokpo harbour were found to be about 3% in COD, 3% in TSS, 5% in VSS, 1% in DIP, 3% in T-P and -1% in DIN.

• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.4
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• pp.679-690
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• 2017

The purpose of this study was to investigate the relationship between neck posture and range of motion and neck disability index(NDI) in young adults with reduced cervical lordosis. This study selected 34 young adults with cervical lordosis reduced (Cobb's angle less than 35 degrees). The assessor measured neck flexion, extension, left lateral flexion, right lateral flexion, left rotation, right rotation and forward displacements of all subjects using cervical of range motion instrument, Then, the NDI was evaluated. After all assessments, degree for cervical lordosis was divided into two groups: bottom group(severe cervical lordosis) and top group(mild cervical lordosis). The bottom group was significantly higher in Cobb's angle, extension, left lateral flexion, right lateral flexion, left rotation, right rotation and forward displacement compared to the top group (p<.05). There was no significant difference between the two groups in flexion, NDI(p >.05). In comparison of subscale of NDI, top group was significantly higher in pain, lifting, and headache than bottom group (p <.05). In correlation analysis, Cobb's angle showed significant positive correlation with flexion, extension, left lateral flexion, right lateral flexion, left rotation and right rotation(p<.05), and showed significant negative correlation with forward displacement, NDI(p<.05). Cobb's angle showed a significant negative correlation with pain, lifting, and headache of subscale of NDI(p<.05). The findings of this study potentially suggest that neck posture may affect the cervical range of motion and pain.