• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.321-322
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• 2006

In many manufacturing processes such as web formation, manufacturing of paper and nonwoven, fabric weaving, etc., planar sheets are transported and at the same time appropriate tension is imposed. The input material rolled up on beams is fed by unwinding the beam and the processed is then taken up on beams by winding it. While processed, the planar sheets are thrown under the processing load of impulse form, which causes irregular thickness of the processed sheet. To improve the quality of the product, a dynamic model is needed and the dynamic characteristics is to be analyzed by simulation. This study shows that density variation dynamics of the in-process-sheet in the machine direction can be described at each moment of disturbing impacts in forms of difference equations, while the impacts and tension, the time-dependency of the material properties were taken into account. Simulation showed the most serious variation of the density occurred in the process starting phase. The starting velocity curve with step form showed the least variation of the density. As the time order of the function of the starting velocity cure becomes higher, the density variation gets greater.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 춘계학술대회 논문집
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• pp.2114-2119
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• 2008

When a train enters into a tunnel, a compression wave is generated by a front nose and a expansion wave is generated by a rear nose each other. Because the compression wave and expansion wave have interactions with the train in a tunnel repeatedly, the internal pressure of the train is dramatically varied. And this pressure variation gives passengers discomfort like ear-ache. In this paper, we had measured the internal pressure variation of TTX developed and being on Test-Running in Honam line and made an analysis of pressure variation rate. As a result, the internal pressure variation was different as to the length of tunnel. Though the entering velocity of TTX is similar on test tunnels, on the short tunnel, the pressure drop was lower then that of the long tunnel. And it was expected that the rates of internal pressure variation would be exceeded the limits on 160km/h entering velocity.

• 한국환경과학회지
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• 제11권3호
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• pp.191-199
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• 2002

In this study, water protection reservoir is selected as the target which is located at the estuary of Taehwa river to analyze and examine the effects of hydraulic structure on river environment. This study aims at the definition of factors which cause the change of ecological environment of river due to the effects of the sediment protection reservoir, and the proposal of the direction of environmental friendly river space development through the analysis and examination of stream variation conditions and riverbed variation characteristics among many effects of hydraulic structure on river environment before and after removal of the sediment protection reservoir when design flow is yielded. Firstly, in case of removal the existing sediment protection reservoir, the hydraulic variation characteristics like depth drop due to removal of the sediment protection reservoir are thought of little because it is examined that depths drop with about 0.01m and 0.01~0.56m when low flow is yielded and design flood yielded, respectively. Nextly, as the examination result of the variation characteristics of flow velocity in case of removal the existing sediment protection reservoir, it is thought that the concern about riverbed erosion is not serious according to the analyzed result as the mean velocity of the channel section where the velocity varies in case of removal the sediment protection reservoir is about 0.07~1.36m/s when low flow is yielded, and is about 1.02~2.41m/s when design flood is yielded despite riverbed erosion is concerned as it is examined that flow velocity is getting increase as about 0.01m/s when low flow is yielded and about 0.01~0.44m/s when design flood is yielded. Lastly, from the prediction result of riverbed variation for each flow amount condition before and after removal the sediment protection reservoir, it is known that the variation range of riverbed is nearly constant when flow amount of the channel exceeds a specific limit as it is analyzed that the more flow amount, the more erosion and sediment in the channel section of down stream part of the sediment protection reservoir and the sediment protection reservoir~Samho-gyo, and the variation ranges according to flow amount between flood condition and design flood condition have little difference in the channel section of the upstream of Samho-gyo.

• 로봇학회논문지
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• 제5권1호
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• pp.32-40
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• 2010

This paper proposes the technique of estimating the pipe thickness using the measured group velocity. To measure the group velocity from the accelerometer data in the frequency domain, Wigner-Ville distribution is utilized, which interprets the waveform of the shock wave. Using this measured group velocity, this paper proposes the technique to estimate the thickness of pipes with the impact on the pipe. The group velocity is estimated by the modeling correlation between the group velocity and the thickness of the pipe based on the propagation velocities. The correlation model between thickness and group velocity has been proved through the real experiments. The measured group velocity in the frequency-domain is the maximum at the center frequency of the bending waves in the modeling of the group velocity. In addition to these, a smoothing technique for analyzing lamb wave Wigner-Ville distribution has been introduced to improve the reliability of the data acquisition.

• International Journal of Fluid Machinery and Systems
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• 제7권2호
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• pp.68-79
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• 2014

The type of turbine developed is based on the very low head of water potential source for the electric power production. The area of research is focused for the axial water turbine that can be applied at the simple site open channel with has a very low cost and environmental impact compared to the conventional hydro installation. High efficiency of axial turbine which applied to the very low potential head will made this type of turbine can be used at wider potential site. Existing irrigation weir and river area will be the perfect site for this turbine. This paper will compare the effects of the variation of swirl velocity criterion during the design of the blade of guide vane and rotor of the turbine. Effects of the swirl velocity criterion is wider known as a vortex conditions (free vortex, force vortex and swirl velocity constant), and the free vortex is the very popular condition that applied by most of turbine designer, therefore will be interesting to do a comparison against other criterion. ANSYS Fluent will be used for simulation and to determine the predictive performance obtained by each of design criteria.

• 지구물리와물리탐사
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• 제19권1호
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• pp.29-36
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• 2016

최근 셰일 저류층의 암석물리학적 모델(Rock Physics Model)에 대한 연구가 활발히 진행되고 있다. 셰일 저류층에서는 케로젠(Kerogen)과 GOR (Gas-Oil Ratio)을 통해서 숙성도를 파악할 수 있는데, 케로젠에 대한 암석물리학적 모델연구는 활발히 진행된 반면, GOR 변화에 대한 셰일 저류층 연구는 아직 미미하다. 따라서 이 연구에서는 GOR 및 케로젠 변화에 따른 속도 및 밀도 변화와 AVO (Amplitude Variation with Offset) 반응을 분석하였다. 판상구조로 이루어진 셰일은 수직 가로 등방성(Vertical Transverse Isotropy; VTI) 성질을 갖기 때문에 Backus averaging 기법을 적용하여 셰일 저류층의 속도 및 밀도를 도출하였고 이를 기반으로 AVO 반응을 분석하였다. GOR변화에 대해서는 속도 변화가 작았지만 케로젠 함량에 따른 속도 변화는 상대적으로 크게 나타났다. 중질오일과 경질오일을 구분할 수 있는 GOR이 180 (Litre/Litre)일 때에는 케로젠의 부피비가 5%에서 35%으로 증가할 때 층에 대해 수직방향인 P파 속도가 51%까지 증가하였다. 즉, 속도 구분을 통해 케로젠의 숙성도를 파악하는데 도움을 줄 수 있다. 한편, 가스와 오일을 합친 유체의 비율이 클 때에는 GOR 변화에 따른 속도 변화가 상대적으로 크게 나타났다. 케로젠의 부피비가 5%일 때에는 중질오일(GOR 40)에서의 층에 대해 수직방향인 P파 속도가 $1.46km/s^2$로 측정되었지만 경질오일(GOR 300)일 때에는 $1.36km/s^2$로 측정되었다. AVO 반응을 분석해본 결과, GOR과 케로젠 함량을 변화시켜도 포아송 비의 변화량이 작게 나타났으므로 Class 4의 양상이 나타났다. 이를 통하여 셰일 저류층에서는 Class 4의 양상이 나타날 수 있음을 확인할 수 있었다.

• 지구물리
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• 제5권2호
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• pp.87-97
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• 2002

기상청 광대역 관측소에서 2000~2001년 포착된 원거리 지진들의 종파 초동 시간의 상대적 도달 시간차이를 분석하여 관측소 하부 지각구조차이에 의한 평균 도달시간이상을 도출하였다. 각 광대역 지진 관측소에서 측정되어진 종파의 상대적 도달시간차이들은 최대 1.5 초로 측정되었다. 각 관측소들의 평균적인 도달시간이상은 최대 0.6초의 차이를 보이며 향후 지진요소 결정 시 이런 차이를 보정하여 주면보다 정밀한 지진요소를 산출할 수 있을 것이다. 각 관측소의 속도 대비차원에서는 최대-4~4%의 속도 대비를 가질 수 있는 것으로 추정되었다. 전반적으로 서울, 춘천, 강릉, 울진, 그리고 울릉도 광대역 관측소에서는 상대적으로 0.05~0.3초 늦은 평균도달시간 이상을 보이며 속도대비로는 0~4% 늦은 것으로 계산되었다. 한편 서산, 대전, 광주, 대구, 서귀포, 그리고 부산 광대역 관측소에서는 0.05~0.3초 빠른 평균도달시간 이상을 보여주며 속도대비로는 약 0~4% 빠른 것으로 계산된다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.343-346
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• 2003

In order to discuss the availability of the hydrostatic guideway driven by the coreless linear motor to ultra precision machine tools, a prototype of guideway is designed and tested in this research. A coreless linear DC motor with the continuous force of 156 N and a laser scale with the resulution of 10 nm are used as the feeding system. The experiments are performed on the static stiffness. motion accuracy, positioning accuracy. microstep response and variation of velocity. The guideway has the infinite axial stiffness within 50 N of applied load, and has 0.08 ${\mu}{\textrm}{m}$ of linear motion error and 0.1 arcsec of angular motion error. It also has 0.21 ${\mu}{\textrm}{m}$ of positioning error and 0.09 ${\mu}{\textrm}{m}$ of repeatability, and it shows the stable response against the 10 nm resolution step command. The velocity variation of feeding system is less than 5%. From these results, it is confirmed that the hydrostatic guideway driven by the coreless linear motor is very useful for the ultra precision machine tools.

• International Journal of Precision Engineering and Manufacturing
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• 제6권2호
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• pp.55-60
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• 2005

In order to develop the hydrostatic guideways driven by a core less linear motor for ultra precision machine tools, a prototype of guideway is designed and tested. A coreless linear DC motor with a continuous force of 156 N and a laser scale with a resolution of 0.01 ㎛ are used in the system. Experimental analysis on the static stiffness, motion errors, positioning error and its repeatability, micro step response and velocity variation of the guideway are performed. The guideway shows infinite stiffness within 50 N applied load in the feed direction, and by the motion error compensation method using the Active Controlled Capillary, 0.08 ㎛ linear motion error and 0.1 arcsec angular motion error are acquired. The guideway also reveals 0.21 ㎛ positioning error and 0.09 ㎛ repeatability, and it shows stable responses following a 0.01 ㎛ resolution step command. The velocity variation of feeding system is less than 0.6 ％. From these results, it is estimated that the hydrostatic guideway driven by a coreless linear motor is very useful for the ultra precision machine tools.

• 한국정보통신학회논문지
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• 제10권2호
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• pp.276-282
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• 2006

본 연구에서는 구조가 단순한 PID 제어기의 장점을 살리고, 시스템 파라메터의 변동에 대하여 강인성 성능을 내는 온라인 적응 PID 제어 시스템을 개발하고자 한다. 또한, 제안된 적응 제어 시스템의 초기 제어 구간에서 안정한 스타트-엎(start-up)을 보장하기 위하여 초기 제어기의 이득을 적절한 이득으로 설정하고, 그 이득의 변화량을 경사 감소법에 의하여 학습하는 방법으로 수정 제안하고자 한다. 제안된 적응 PID제어기의 성능 평가를 위하여 비선형 DC 모터의 가변 속도제어에 적용하고, 결과를 모의실험을 통하여 보이고자한다.