• Applied Microscopy
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• 제25권3호
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• pp.99-107
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• 1995

The morphological changes of primary solid particles as a function of process time on hypereutectic Al-15.5wt%Si alloy during semi-solid state processing with a shear rate of $200s^{-1}$ are studied. In this alloy, it was observed that primary Si crystals are fragmented at the early stage of stirring and morphologies of primary Si crystals change from faceted to spherical during isothermal shearing for 60 minutes. To understand the role of Al dissolved in the primary Si crystal by shear stress at high temperature, lattice parameters of the primary Si crystals are determined as a variation of high order Laue zone(HOLZ) line positions measured from convergent beam electron diffraction(CBED) pattern. The lattice parameter of the primary Si crystal in the rheocast Al-15.5wt%Si alloy shows tensile strain of about 5 times greater than that of the gravity casting. Increase of the lattice parameter by rheocasting is due to the increased amount of Al dissolved in the primary Si crystal accelerated by shear stress at high temperature. The amounts of solute Al in the primary Si crystal are measured quantitatively by EPMA method to confirm the CBED analysis.

• 예술인문사회 융합 멀티미디어 논문지
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• 제5권2호
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• pp.215-222
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• 2015

본 논문에서는 중앙에 경사 균열이 있는 시편을 원형편광기에 설치하여 인장하중을 가한 후 나타나는 등색프린지로부터 디지털 영상처리기법을 사용하여 광탄성 프린지를 2배로 증식하여 세선처리한 후, 이로부터 응력확대계수를 측정하였다. 경사균열 시편으로부터 광탄성 법을 이용하여 응력확대계수를 구한 후 이론식으로 계산한 값과 비교하였다. 실험 결과는 이론값에 근접하였으며 광탄성 법으로 응력확대계수를 정밀하게 측정할 수 있는 가능성을 제시하였다.

• 동력기계공학회지
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• 제20권1호
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• pp.69-74
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• 2016

The local heat transfer and pressure drops of developed turbulent flows in the convergent channels with square cross-sectional areas along the streamwise distance have been investigated experimentally. Four different parallel angled ribs (a = $30^{\circ}$, $45^{\circ}$, $60^{\circ}$, and $90^{\circ}$) are placed to the one sided wall only, respectively. The ribbed walls are manufactured with a fixed rib height (e)=10 mm and the ratio of rib spacing (p) to height (e) = 10. The measurement was run within the range of Reynolds numbers from 22,000 to 79,000. The result shows that the increases in the Nusselt numbers for the flow attack angles can be seen in the order of $30^{\circ}$, $45^{\circ}$, $60^{\circ}$ and $90^{\circ}$.

• International Journal of Aeronautical and Space Sciences
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• 제18권4호
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• pp.697-708
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• 2017

The complex battlefield environment makes it difficult to intercept maneuvering targets for guided missiles. In this paper, a finite-time convergent (FTC) guidance law based on the second-order sliding mode (SOSM) control theory is proposed to achieve the requirements of stability, accuracy and robustness. More specifically, a second-order sliding mode observer (SMOB) is used to estimate and compensate for the total disturbance of the controlled system, while the target acceleration is extracted from the line-of-sight (LOS) angle measurement. The proposed guidance law can drive the LOS angular rate converge to zero in a finite time, which means that the missile will accurately intercept the target. Numerical simulations with some comparisons are performed to demonstrate the superiority of the proposed guidance law.

• 동력기계공학회지
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• 제18권3호
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• pp.66-72
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• 2014

The local heat transfer and pressure drop of developed turbulent flows in the smooth convergent/divergent channels with rectangular and square cross-sectional areas along the axial distance have been investigated experimentally. The measurement was conducted within the range of Reynolds numbers from 15,000 to 89,000. The channel hydraulic diameter ratios of 0.67 and 1.49 in the rectangular channel with 2 inclined walls and the ratios 0.75 and 1.33 in the square channel with 4 inclined walls are considered. The comparison showed that among the four channels the square divergent channel has the highest thermal performance at the identical mass flow rate, at the identical pumping power, and at the static pressure drop.

• Applied Microscopy
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• 제36권spc1호
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• pp.47-56
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• 2006

Improvements are made to existing primitive cell volume measurement method to provide a real-time analysis capability for the phase analysis of nanocrystalline materials. Simplification is introduced in the primitive cell volume calculation leading to fast and reliable method for nano-phase identification and is applied to the phase analysis of Mo-Si-N nanocoating layer. In addition, comparison is made between real-time and film measurements for their accuracy of calculated primitive cell volume values and factors governing the accuracy of the method are determined. About 5% accuracy in primitive cell determination is obtained from camera length calibration and this technique is used to investigate the cell volume variation in WC-TiC core-shell microstructure. In addition to chemical compositional variation in core-shell type structure, primitive cell volume variation reveals additional information on lattice coherency strain across the interface.

• 한국융합학회논문지
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• 제9권10호
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• pp.141-147
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• 2018

본 연구의 목적은 유도된 발목 근피로 시 테이핑, 스트레칭 그리고 초음파가 융합적 균형능력에 미치는 효과를 알아보는 데 있다. 건강한 성인 남녀 39명이 본 연구에 자발적으로 참여하였다. 발목 근피로 유발 이후 대상자들은 테이핑, 정적 스트레칭 또는 초음파 그룹으로 무작위 선정되었다. 그리고 각 그룹에 해당하는 중재방법이 적용되었다. 균형 능력은 Space Balance 3D를 이용하여 발목 근피로 전과 후 그리고 중재 후에 측정되었다. 균형능력은 그룹 간 유의한 차이는 없었지만(p>.05), 그룹 내 모두에서 유의하게 증가하였다(p<.001). 그러므로 발목 근 피로에 테이핑, 정적 스트레칭 그리고 초음파는 융합적 균형능력에 효과적일 것이다. 향후 연구에서는 다양한 측정변수 측정과 치료적 중재를 적용하여 치료적 효과를 증명할 필요가 있다.

• 한국터널공학회:학술대회논문집
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• 한국터널공학회 2005년도 학술발표회 논문집
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• pp.270-281
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• 2005

An especial attention for old tunnel safety is required on increasing of The various tunnel recently. Specially, the lining investigation method of the old tunnel will be able to presume condition of concrete lining indirectly. Because it is many restriction thought of environment and ground condition investigation method of tunnel lining rear. This study carried out section & convergence measurement of part which was deformed in tunnel lining. It had been observed for the change of tunnel behavior with a continuous measurement. It has been analyzed for a cause of tunnel deformation and inspected for the effect after a repair-reinforcement to tunnel compared with the effect before those by structure analysis. By establishing automatic measurement system after repair-reinforcement to tunnel, it would be accomplished to convergence measurement continually. As a result, it was observed that deflection and deformation of tunnel was convergent. but it should be followed to a continuous maintenance because of unstable ground condition, cause of inner tunnel, environment. The railroad tunnel which was executed a reinforcement of the tunnel lining must investigate the close condition of reinforcement lining and concrete lining.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2000년도 추계학술대회 논문집
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• pp.79-83
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• 2000

A sliding mode fuzzy control (SMFC) with disturbance estimator is applied to design a controller for the third generation benchmark problem on an wind-excited building. A distinctive feature in vibration control of large civil infrastructure is the existence of large disturbances, such as wind, earthquake, and sea wave forces. Those disturbances govern the behavior of the structure, however, they cannot be precisely measured, especially for the case of wind-induced vibration control. Since the structural accelerations are measured only at a limited number of locations without the measurement of the wind forces, the structure of the conventional control may have the feed-back loop only. General structure of the SMFC is composed of a compensation part and a convergent part. The compensation part prevents the system diverge, and the convergent part makes the system converge to the sliding surface. The compensation part uses not only the structural response measurement but also the disturbance measurement, so the SMFC has a feed-back loop and a feed-forward loop. To realize the virtual feed-forward loop for the wind-induced vibration control, disturbance estimation filter is introduced. the structure of the filter is constructed based on an auto regressive model for the stochastic wind force. This filter estimates the wind force at each time instance based on the measured structural responses and the stochastic information of the wind force. For the verification of the proposed algorithm, a numerical simulation is carried out on the benchmark problem of a wind-excited building. The results indicate that the present control algorithm is very efficient for reducing the wind-induced vibration and that the performance indices improve as the filter for wind force estimation is employed.

• 예술인문사회 융합 멀티미디어 논문지
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• 제9권9호
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• pp.797-808
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• 2019

본 연구의 목적은 TV홈쇼핑 광고를 시청하는 동안 일어나는 심리적 반응을 언어적 형태로 수집하고, 수집된 언어자료를 분석하여 광고효과의 측정 가능성을 탐색하는 것이다. 이를 위해 주부와 여자 대학생 40명을 대상으로 긍정평가 광고와 부정평가 광고를 시청하는 동안 나타난 심리적 반응을 사고발성법을 이용하여 언어자료의 형태로 수집하고, 자기보고식 측정으로 광고효과변인들과 광고반응 변인들을 측정하였다. 수집된 언어자료를 KLIWC를 이용하여 분석하여 긍부정평가 광고 간의 차이와 자기보고식 변인들 간의 상관을 살펴보았다. 검증결과, 긍정평가 광고와 부정평가 광고 간에 심리사회학적 변인뿐만 아니라 언어학적 변인에서도 차이가 나타났다. 또한 KLIWC의 다양한 변인들과 광고효과 변인들(구매자극도, 광고태도, 제품태도, 구매의도) 그리고 광고반응 변인들 간에 상관이 나타났다. 이러한 결과는 사고발성법과 KLIWC의 언어분석을 이용하여 TV홈쇼핑 광고 효과를 측정할 수 있는 가능성과 심리적 반응 프로파일을 구성할 수 있는 가능성을 시사하여 준다.