• 대한기계학회논문집A
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• 제34권8호
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• pp.971-980
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• 2010

이 논문은 모바일 로봇이 고정 장애물 또는 움직이는 장애물이 존재하는 환경에서 장애물을 회피하며 운행될 수 있는 제어 알고리즘을 연구하였다. 이 제어 알고리즘은 $D^*$ 알고리즘과, 충돌 위험도 퍼지로직, 이동로봇의 행동결정 퍼지로직을 사용하여 전역경로계획과 지역경로계획을 수행한다. $D^*$ 알고리즘에는 로봇이 이동하는 2 차원 공간을 정방형 격자 분활하여 적용한다. 이 알고리즘은 파이썬 프로그래밍 언어와 이동로봇의 운동방정식을 사용한 시뮬레이션을 통해 검증하였다. 시뮬레이션 결과를 통해 알고리즘을 적용하여 로봇이 이동하는 장애물을 피하거나 모르는 고정 장애물을 피하면서 원하는 위치로 이동하는 것을 볼 수 있다.

• 플랜트 저널
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• 제4권3호
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• pp.66-72
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• 2008

The vibration of steam turbine is caused by Mass unbalance, Shaft misalignment, Oil whip and rubbing etc. But in turbine which is normally operated and maintained, the Mass unbalance component possesses the greatest portion. Our power plant has two steam turbines in capacity of 200 MW and 135 MW respectively and each turbine is supported by 6 journal bearings. However, we had many difficulties because the vibration amplitude of #3 and #4 Bearings was high during the start-up and operation mode change of steam turbine. But, with this study, we completely solved the vibration problem caused by the mass unbalance of #1 steam turbine. Until a recent date, #3 and #4 bearings which support high pressure turbine for #1 steam turbine had shown about $135{\mu}m$ in vibration amplitude (sometimes it increased to $221{\mu}m$ maximum. alarm: 6 mils, trip: 9 mils) at base load. After applying the study, they decreased to about $45{\mu}m$ maximum. It is a result from that we did not change the setting value of bearing alignment and only changed the assembly position of internal parts in Synchro clutch coupling rachet wheel which links between high pressure turbine and low pressure turbine, and increased the internal gap and machining of the Pawl cage surface. In the operation of steam turbine, if the vibration value increases by 1X, we should reduce the vibration of bearing by weight balancing. However, unless the vibration of bearing is declined by the balancing, we will have to disassemble and check the component and find the cause. In this study, we researched the way to lower mass unbalance that is 1X vibration component which has the greatest portion of vibration generated by steam turbine and we got good result by applying the findings of this study.

• 천문학논총
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• 제20권1호
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• pp.143-149
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• 2005

KASI (Korea Astronomy and Space Science Institute) is developing the near-infrared camera system named KASINICS (KASI Near-Infrared Camera System) which will be installed at the 60cm f/13.5 Ritchey-Chretien telescope of the Sobaeksan Optical Astronomy Observatory (SOAO). The camera system is optimized for JHKL bands and has a 6 arcmin FOV. The optical system consists of two spherical mirrors and a 8-position filter wheel. With the exception for the dewar window, all optical elements are cooled inside cryogenic dewar. Since the Offner system is adopted to prevent thermal noises from outside of the telescope primary mirror, the secondary mirror of the Offner system acts as a cold Lyot stop. The optical performance does not change by temperature variations because the Aluminum mirrors contract and expand homogeneously with its mount. We finished the design and fabrication of the optical parts and are now aligning the optical system. We plan to have a test observation on 2006 January.

• 대한치과기공학회지
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• 제33권4호
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• pp.331-337
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• 2011

Purpose: The purpose of this study was to impact of force system change in finger spring that add helical coil one round on orthodontic force. Methods: The following conclusions were drawn from the experiment conducted after bending 90 samples with a CNC wire forming machine while changing the height and lumen size to 1mm - 3mm - 5mm and 2mm - 3mm - 4mm respectively in the coil of the force system in finger spring added with one wheel of helical coil of 18-8 stainless steel round wire (${\Phi}0.5mm$, spring hard) from Jinsung Co. in domestic market under the following conditions: Laboratory name = Instron 5942; Temperature($deg^{\circ}C$) = 18.00; Humidity(%) = 50.00; Rate 1 = 10.00000 mm/min; Compressive extension = 5.0mm. Results: When Coil height is 1, 3, 5mm and lumen size is 2, 3, 4mm reduce finger spring as mean value of compressive extension occasion maximum load(mN) increases as coil height rises, and lumen size grows to 5.0mm. And was expose that compressive load(mN) increases as coil position of finger spring rises and increase as lumen size is decrescent. Conclusion: As the adherence height of coil was raised from 1mm through 3mm to 5mm, compressive load increased. As the lumen size increased from 2mm through 3mm to 4mm, compressive load decreased. Therefore, these results suggest that it is desirable to lower the coil height and enlarge the lumen size to enhance the biomechanical efficiency of finger spring when manufacturing the finger spring for removable orthodontic devices.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.232-235
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• 2008

The vibration of steam turbine is caused by Mass Unbalance, Shaft Misalignment, Oil Whip and Rubbing etc. but in turbine which is normally operated and maintained, the Mass Unbalance component possesses the greatest portion. Our power plant has two steam turbines in capacity of 200MW and 135MW respectively and each turbine is supported by 6 journal bearings. However, we had many difficulties because the vibration amplitude of No 3 and 4 Bearings was high during the start-up and operation mode change of steam turbine. But, with this study, we completely solved the vibration problem caused by the mass unbalance of No 1 steam turbine. Until a recent date, No 3 and 4 bearings which support high pressure turbine for No 1 steam turbine had shown about 135${\mu}$m in vibration amplitude (sometimes it increased to 221${\mu}$m maximum. alarm: 6mils, trip: 9mils) at base load. After applying the study, they decreased to about 40${\mu}$m maximum. It is a result from that we did not change the setting value of Bearing Alignment and only changed the assembly position of internal parts in Synchro Clutch Coupling Rachet Wheel which links between high pressure turbine and low pressure turbine, and increased the internal gap and machining of the Pawl stopper surface. In the operation of steam turbine, if the vibration value increases by 1X, we should reduce the vibration of bearing by weight balancing. However, unless the vibration of bearing is declined by the balancing, we will have to disassemble and check the component and find the cause. In this study, We researched the way to lower mass unbalance that is 1X vibration component which has the greatest portion of vibration generated by steam turbine and We got good result by applying the findings of this study.

• 전기학회논문지
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• 제57권9호
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• pp.1606-1611
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• 2008

Recently, The diagnosis techniques of electric facilities are developed on live line. This paper describes the discharge characteristics of polymer insulator(EPDM A type). Keeping the facilities in good working order, the goal of this paper will provide the information to enable user to easily judge conditions of facilities on the spot. The performance of polymer insulator is assessed from the KS C IEC 60270 and CEA LWIWG-01(96)(Tracking Wheel Test). As the results, UV generation patterns of polymer insulator grow like a jellyfish shape follow the ramping voltage. Discharging UVs are detected at about 31.25% of breakdown voltage. Just then, dimension of UV image is about $0.84cm^{2}$. The dimension of max. UV image is about $297.4cm^{2}$ at $160kV(V_{bd})$. The position of UV generation due to surface discharge of polymer insulator is the center of insulator in the early, then moved the ground side and the last, UV image moved through the junction part of source side. Surface of aged polymer insulator is cracked and faded due to arc. UV absorption spectrum of polymer insulator are appeared the C-H bond of scissoring vib. at $1014cm^{-1}$ and C=O bond of recombination structure. Also, recombined UV absorption peak such as C-H, N-H, and O-H is detected at the $3321cm^{-1}$. Through the paper, there are inspection data which are the relations between surface discharge of polymer insulator and UV detecting image.

• Tribology and Lubricants
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• 제33권1호
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• pp.1-8
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• 2017

Drag torque reduction in a wet clutch pack is a key aspect of the design process of the dual clutch transmission (DCT) system. In order to reduce the drag torque caused by lubricant shear resistance, recently developed wet clutch pack systems of DCT, as well as automatic transmission and other four-wheel drive (4WD) couplings, frequently utilize wavy wet clutch pads. Therefore, wavy shape of friction pad are made on the groove patterns like waffle pattern for the reduction of drag torque. Additionally, the groove patterns are designed with larger channels at several locations on the friction pad to facilitate faster outflow of lubricant. However, channel performance is a function of the waviness of the friction pad at the location of the particular channel. This is because the discharge sectional area varies according to the waviness amplitude at the location of the particular channel. The higher location of the additional channel on the friction pad results in a larger cross-sectional area, which allows for a larger flow discharge rate. This results in reduction of the drag torque caused by the shear resistance of DCTF, because of marginal volume fraction of fluid (VOF) in the space between the friction pad and separator. This study computes the VOF in the space between the friction pad and separator, the hydrodynamic pressure developed, and the shear resistance of friction torque, by using CFD software (FLUENT). In addition, the study investigates the dependence of these parameters on the location and waviness amplitude of the channel pattern on the friction pad. The paper presents design guidelines on the proper location of high waviness amplitude on wavy friction pads.

• 대한기계학회논문집
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• 제17권6호
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• pp.1497-1508
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• 1993

본 논문에서는 새로운 이동로봇의 제어구조로서 범용 개인용 컴퓨터를 주축으 로 설계되는 이동로봇 제어시스템에 대해 기술하고자 한다. 이 제어시스템에서는 자율 이동로봇의 경로제어에 필수적인 경로계획기. 경로추종 제어 알고리즘, 자기 위 치 추정기 그리고 휠 제어기 등을 모듈별로 연결/구성하였으며, 본 연구실에서 연구용 으로 개발한 휠 구동 지능형 이동 로봇 LCAR-90의 시스템 묘사와 함께 제어 시스템의 하드웨어적 설계배경에 대해 기술하고, 제 3장에서는 제어시스템의 필수적인 요소중 하나인 이동로봇의 자기 위치 추정방법과 제어 시스템의 핵심부인 경로추종 제어에 관한 새로운 알고리즘을 적용한 결과에 대해 논의한다. 최종적으로 제 4장에서는 본 연구를 통해 얻은 결론을 기술하였다.

• 한국도로학회논문집
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• 제6권1호
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• pp.25-36
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• 2004

국내 고속국도 및 일반국도의 약40%, 98%가 아스팔트 포장으로 구성되어 있으며 아스팔트 포장의 주요 파손 형태는 러팅(rutting) 및 균열이다. 파손이 심한 아스팔트 포장에 공용성이 좋은 것으로 알려져 있는 UTW(Ultra-Thin Whitetopping, 이하 중 신 콘)가 국내 도로의 유지보수 공법으로 적용될 수 있는가를 판단하였다. 본 논문은 경기도 폐도에 시험 시공된 중 신 콘 포장에서의 정적하중재하실험을 통하여 교통하중 및 환경하중 조건에 따른 중 신 콘의 거동 분석 결과이다. 콘크리트 두께를 50, 100, 150mm로 하여 두께에 따른 거동을 분석한 결과, 콘크리트 두께가 50mm일 때 콘크리트 하부에서 발생하는 인장 변형률이 급격하게 증가한다는 것을 알 수 있었다. 또한 계절별 실험을 통해 포장 온도가 중 신 콘 거동에 미치는 영향이 큰 것을 알 수 있었다. 하중재하위치에 따른 거동분석 결과에서는 슬래브 중앙부와 줄눈부에서 약 25cm 떨어진 지점부터 하중이 재하될 때 중앙부와 줄눈부에 영향을 미치기 시작하였고 이 때, 최대 인장 변형률의 75%까지 변형률이 발생함에 따라 줄눈간격 결정에 주의를 요해야 할 것으로 판단되었다.

• 대한기계학회논문집A
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• 제35권11호
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• pp.1391-1398
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• 2011

본 논문은 장비의 동작분석기법을 이용하여 운전자가 핸들을 돌릴 때 팔의 관절 운동에 대한 생체역학적 해석을 수행하였다. 모형 운전석에서 운전자가 핸들을 돌릴 때 모션 캡쳐(motion capture) 시스템을 이용하여 팔의 3차원 운동궤적을 구하고, 이 결과를 이용하여 팔의 근-골격계 모델에 대한 역기구학 해석과 역동역학 해석을 수행함으로써 팔 관절의 변위와 관절 토크의 크기를 계산하였다. 각 관절의 회전 운동은 동시에 복합적으로 발생하며, 관절 운동의 크기의 관점에서 팔꿈치 관절의 회내-회외, 어깨 관절의 내전-외전, 굴곡-신전, 손목 관절의 굴곡-신전 등이 주요한 운동임을 확인할 수 있었다. 모형 운전석의 운전 자세, 핸들의 각도 및 좌석에 대한 상대적 위치와 관련된 설계변수에 대한 관절운동의 민감도 해석을 통하여 운전 자세와 핸들의 위치가 조향 동작에 미치는 영향을 정량적으로 분석하였다.