• 한국가시화정보학회지
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• 제3권2호
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• pp.63-70
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• 2005

Birds and insects flap their wings to fly in the air and they can change their wing motions to do steering and maneuvering. Therefore, we created various wing motions with the parameters which affected flapping motion and evaluated the aerodynamic characteristics about those cases in this study. As the wing rotational velocity was fast and the rotational timing was advanced, the measured aerodynamic forces showed drastic increase near the end of stroke. The mean lift coefficient was increased until angle of attack of $50^{\circ}$ and showed the maximum value of 1.0. The maximum mean lift to drag ratio took place at angle of attack of $20^{\circ}$. Flow fields were also visualized around the wing using particle image velocimetry (PIV). From the flow visualization, leading-edge vortex was not shed at mid-stroke until angle of attack of $50^{\circ}$. But it was begun to shed at angle of attack of $60^{\circ}$.

• Nuclear Engineering and Technology
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• 제55권6호
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• pp.2325-2334
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• 2023

To study the lubrication performance of tilting-pad thrust bearing (TPTBs) during start-up in nuclear pump, a hydrodynamic lubrication model of TPTBs was established based on the computational fluid dynamics (CFD) method and the fluid-structure interaction (FSI) technique. Further, a mesh motion algorithm for the transient calculation of thrust bearings was developed based on the user defined function (UDF). The result demonstrated that minimum film thickness increases first and then decreases with the rotational speed under start-up condition. The influence of pad tilt on minimum film thickness is greater than that of collar movement at low speed, and the establishment of dynamic pressure mainly depends on pad tilt and minimum film thickness increases. As the increase of rotational speed, the influence of pad tilt was abated, where the influence of the moving of the collar dominated gradually, and minimum film thickness decreases. For TPTBs, the circumferential angle of the pad is always greater than the radial angle. When the rotational speed is constant, the change rate of radial angle is greater than that of circumferential angle with the increase of loading forces. This study can provide reference for improving bearing wear resistance.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 학술회의 논문집 정보 및 제어부문 B
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• pp.396-399
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• 2003

This paper proposes a simple digital image stabilization(DIS) algorithm for roll motion, which has not been compensated in the 2-axes mechanical stabilization system, using aero-crossing of the rotational motion vectors. The 2-axes stabilization system cannot stabilize rolled images, which causes the deteriorated performance of the object detection and recognition. In this paper, we propose the rotational motion stabilization algorithm which estimates and compensates global motion in terms of rotational center and rotational angle. Both the synthetic images with undesirable rotational disturbance and the real images from 2-axes stabilization system are used to evaluate the proposed algorithm. The results show that our proposed algorithm suppresses the undesirable rotational disturbance effectively.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 추계학술대회 논문집
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• pp.861-866
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• 1996

The Non-Circular Gears is more advantage than other machinery using link and cam in the automation equipment. We designed Non-Circular Gears for a velocity of inequalty rotational equipment according to the variation of pressure angle, radius of curvature etc., and studied about pitch curve.

• 한국광학회지
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• 제19권4호
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• pp.302-309
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• 2008

컴퓨터 전산모의와 회전자를 이용한 실험을 통하여 회전변위에 따른 반복사인격자 한 쌍이 만드는 무아레 무늬의 변화를 세밀하게 조사하여 반복사인격자가 겹쳐서 동시에 생기는 두 가지의 서로 다른 무아레 무늬를 사용하는 작은 회전변위를 측정하는 가시적 방법을 보여준다. 이 무아레 무늬는12도 이상의 큰 각도 측정에 유용한 장주기의 넓고 긴 직선무늬와 12도 이하의 작은 각도 측정에 유리한 좁고 짧은 복잡한 직선무늬로 이루어져 있다. 그리고 무아레 무늬의 회전방향에 따라 회전변위의 회전방향도 동시에 가시적으로 판별할 수 있다.

• Bulletin of the Korean Chemical Society
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• 제16권5호
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• pp.436-438
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• 1995

Based on the collisional time-correlation function approach a general analytical expression has been derived for the double differential cross-section with respect to the scattering angle and the final rotational energy, which can be applied to molecules with non-zero electronic orbital angular momentum after collision with fast hydrogen atoms. By integrating this expression another very simple expression, which gives the final rotational distribution as a function of the rotational quantum number, has also been derived. When this expression is applied to NO(2Π1/2, v'=1) and NO(2Π3/2, v'=1, 2, 3), it can reproduce the experimental rotational distribution after collision with fast H atom very well. The average rotational quantum number and average rotational energy using this expression are also in good agreement with those deduced from the experimental distributions.

• Journal of Oral Medicine and Pain
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• 제21권2호
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• pp.369-382
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• 1996

The author performed this study to investige the relationship between condylar movements recorded with Pantronicⓡ and mandibular rotational torque movements with BioEGNⓡ. For this study 56 patients with Temporomandibular disorders(TMD) and 30 dental students without any masticatory signs and symptoms were selected as patients group and control group, respectively. The items recorded with Pantronicⓡ(Denar Corp., USA) were immediate side-shift, progressive side-shift, angle of orbiting path, protrusive path and PRI. BioEGNⓡ(Bioelectric gnathography, Bioresearch Inc., USA) were used to measure the amounts of mandibular rotational torque movements in frontal and horizontal plane, and the distance of mandibular translation at incisal area. Amount of mandibular rotational torque movement depicted between the condyles was automatically analysed by angle and difference in frontal and horizontal plane. The obtained data were processed with SAS program and the conclusion of this study were as follows : 1. Mean values of items between patients group and control group in Pantronic measurements were not significantly different except in left protrusive path and in Pantronic Reproducibility Index(PRI). There were no significant difference of condylar paths by preferred chewing side and affected side between the two groups. 2. The amount of mandibular rotational torque movements were differed in frontal angle and difference on protrusion, and in frontal and in horizontal difference on left excursion between the two groups. But the amounts of translatory movements were actually same on all eccentric movements. 3. The amount of mandibular rotational torque movements with splint mere almost not changed from those without splint, with the exception of in horizontal measurements on protrusion. 4. The correlations of items between in Pantronic measurements and in BioEGN measurements wert not consistently, significant, however, generally the ISS related significantly with horizontal torque movement positively, and with frontal torque movement negatively on the contrary, the PSS showed positive correlation with frontal torque movement, and negative correlation with horizontal torque movement.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권3호
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• pp.149-155
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• 2006

This paper presents a torsional micromirror detached from PZT actuators (TMD), whose rotational motion is achieved by push bars in the PZT actuators detached from the micromirror. The push bar mechanism is intended to reduce the bending, tensile and torsional constraints generated by the conventional bending bar mechanism, where the torsional micromirror is attached to the PZT actuators (TMA). We have designed, fabricated and tested prototypes of TMDs for single-axis and dual-axis rotation, respectively. The single-axis TMD generates the static rotational angle of $6.1^{\circ}$ at 16 VDC, which is 6 times larger than that of single-axis TMA, $0.9^{\circ}$. However, the rotational response curve of TMD shows hysteresis due to the static friction between the cover and the push bar in the PZT actuator. We have shown that 63.2% of the hysteresis is due to the static friction caused by the initial contact force of the PZT actuaor. Without the initial contact force, the rotational response curve of TMD shows linear voltage-angle characteristics. The dual-axis TMD generates the static rotational angles of $5.5^{\circ}$ and $4.7^{\circ}$ in x-axis and y-axis, respectively at 16 VDC. The measured resonant frequencies of dual-axis TMD are $2.1\pm0.1$ kHz in x-axis and $1.7\pm0.1$ kHz in y-axis. The dual-axis TMD shows stable operation without severe wear for 21.6 million cycles driven by 16 Vp-p sinusoidal wave signal at room temperature.

• Elastomers and Composites
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• 제43권1호
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• pp.25-30
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• 2008

자동차 부싱은 차체로 전달되는 하중을 줄여주는 역할을 하는 자동차 현가장치의 주요 부품으로 바깥쪽 슬리브와 안쪽의 축 사이에서 가운데가 비어 있는 실린더의 형상을 가진다. 차축에 작용되는 힘과 모멘트에 대한 부싱의 상대변위 및 변형각도는 점탄성 성질을 나타내며, 부싱에서 힘과 모멘트와 이에 대한 변위와 변형각도의 관계는 다물체 동역학 시뮬레이션에 매우 중요하다. 본 연구는 자동차 부싱의 회전방향 모드에 대한 모멘트와 변형각도의 점탄성 관계를 변형각도에 의존하는 모멘트 완화함수를 통하여 부싱모델을 완성하였으며, 완성된 점탄성 부싱 모델은 회전방향 모드에 대한 실험값과 비교하여 검증하였다.

• Steel and Composite Structures
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• 제26권1호
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• pp.67-78
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• 2018

The application of rib stiffeners is common on steel connections, with regard to the stiffened angle connection, experimental results about the influence of stiffeners under monotonic and cyclic loading are very limited. Consequently, this paper presents the experimental investigation on four types angle connections with or without stiffener under static loading and another four type stiffened angle connections subjected to cyclic loading. The static experimental result showed that the rib stiffener weld in tension zone of the connection greatly enhanced its initial rotational stiffness and flexural strength. While a stiffener was applied to the compression zone of the connection, it had not obvious influences on the initial rotational stiffness, but increased its flexural strength. The moment-rotation curves, skeleton curves, ductility, energy dissipation and rigidity were evaluated under cyclic loading. Stiffened top-and-seat angle connections behaved as semi-rigid and partial strength, and rotation of all stiffened angle connections exceeded 0.04rad. The failure modes between monotonic and cyclic loading test were completely different and indicated certain robustness.