• 대한조선학회논문집
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• 제41권4호
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• pp.38-44
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• 2004

The motion response analysis of a submerged elliptic cylinder in waves is presented and the elliptic cylinder is a simplification of the section of submarine in this paper. The method is based on boundary integral method and two-dimensional 3 degree motions are calculated in regular harmonic waves. The fully nonlinear free surface boundary condition is assumed in an numerical domain and this solution is matched along an assumed boundary as a linear solution composed of transient Green function, The large amplitude motions of an elliptic cylinder are directly simulated and effects of wave frequency, wave amplitude and the distance from buoyancy center to gravity center are discussed.

• Journal of Astronomy and Space Sciences
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• 제24권4호
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• pp.315-326
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• 2007

최근에 제안된, 이웃하는 타원 궤도의 상대운동에 대한 몇 가지 양함수형 해를 분석하였다. 이 해를 이용한 상대운동 결과를 일반 선형화 운동 방정식의 해석적 해와 비교했다. 수치계산 결과를 위한 초기 조건은 Hill-Clohessy-Wiltshire(HCW) 운동방정식에 의한 해의 역함수로 구했다. 기준 궤도의 차이에도 불구하고 상대적으로 작은 이심률의 궤도 일 경우에는 타원 상대운동 궤도와 원 상대운동 궤도의 결과는 근접했다. 주위성의 궤도가 상대적으로 큰 이심률을 가질 경우에는, 기본 궤도로 원 궤도를 이용하는 HCW 운동방정식은 다른 타원 상대운동 궤도 방정식의 해보다 상대적으로 큰 오차를 갖는다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 추계학술대회 논문집
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• pp.177-180
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• 2000

In this paper, we studied efficiency improvement of linear ultrasonic motor using projection. The principle of ultrasonic motor is to use an elliptic motion generated at the side of the vibrator, and the elliptic motion of the ultrasonic motor was obtained by complex oscillation of L$_1$-B$_4$ mode. As the experimental results, the efficiency of linear ultrasonic motor without projection was 1.52[%] when applied voltage was 56[V] in resonance frequency 58.4[kHz]. The efficiency of linear ultrasonic motor using projection was 3.36[%] when applied voltage was 56[V] in resonance frequency 58.4[kHz]. The efficiency was improved by projection.

• Journal of Mechanical Science and Technology
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• 제17권8호
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• pp.1234-1245
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• 2003

An experimental study was carried out to investigate the reduced frequency effect on the near-wake of an elliptic airfoil oscillating in pitch. The airfoil was sinusoidally pitched around the center of the chord between -5$^{\circ}$and ＋25$^{\circ}$angles of attack at an airspeed of 3.4 m/s. The chord Reynolds number and reduced frequencies were 3.3 ${\times}$10$^4$, and 0.1, 0.7, respectively Phase-averaged axial velocity and turbulent intensity profiles are presented to show the reduced frequency effects on the near-wake behind the airfoil oscillating In pitch. Axial velocity defects in the near-wake region have a tendency to increase in response to a reduced frequency during pitch up motion, whereas it tends to decrease during pitch down motion at a positive angle of attack. Turbulent intensity at positive angles of attack during the pitch up motion decreased in response to a reduced frequency, whereas turbulent intensity during the pitch down motion varies considerably with downstream stations. Although the true instantaneous angle of attack compensated for a phase-lag is large, the wake thickness of an oscillating airfoil is not always large because of laminar or turbulent separation.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 하계종합학술대회 논문집(4)
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• pp.202-205
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• 2000

In this paper we propose an algorithm that detects, tracks a moving object, and classify whether it is human from the video clip captured under the fixed video camera. It detects the outline of the moving object by finding out the local maximum points of the modulus image, which is the magnitude of the motion vectors. It also estimates the size and the center of the moving object. When the object is detected, the algorithm discriminates whether it is human by segmenting the face. It is segmented by searching the elliptic shape using Hough transform and grouping the skin color region within the elliptic shape.

• Journal of Theoretical and Applied Mechanics
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• 제2권1호
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• pp.51-70
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• 1996

This study is generalization of the study of Miles[Physica 11D, 1984, pp.309-323]on the resonant motion of a spherical pendulum, which is equivalent to a particle on a spherical container subject to a linear, horizontal excitation. This study covers an arbitrary shape of container and a more general excitation (horizontal but elliptic motion). The averaging method is applied to reduce the governing equations to an autonomous system with cubic nonlinear terms, under the assumption of small amplitude of the container motion. It is shown that both the container shape and the excitation pattern affect the particle dynamics. Under the linear excitation, the anharmonic motion of the particle is possible only for a certain finite range of the parameter a controling the container shape. Stability of the particle's harmonic motion is also influenced by the excitation pattern; as the excitation trajectory becomes closer to a circle, the particle's motion has a stronger tendency to become stable and to follow the rotational direction of the excitation. Under a circular excitation, the motion is always stable and circular with the same rotational direction as the excitation. Analogy between the present model and that of the surface wave inside a circular is studied quantitatively.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 춘계학술대회 논문집
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• pp.837-841
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• 1996

It is the eccentricity that determines most of the characteristics of the elliptic gears. Accoding to the theoretical tooth profiles, two pairs of the elliptic gears were manufactured by using CNC wire cutting machine. For harmonious rotating motion, it is necessaryto consider operating pressure angle and module not to generate undercut. The characteristics of vibration were investigated by analyzer.

• 한국정밀공학회지
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• 제15권12호
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• pp.37-47
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• 1998

This study discusses the feed dog feeding mechanism of an industrial lock stitch sewing machine, which is a good example to study a machine kinematics. The feed dog feeding mechanism makes the fabrics directly be fed by an elliptic motion of the feed dog that is moved by a rotation of the top shaft and controlled by the feeding control mechanism. This study makes mathematical expressions of machine's motion in the feed dog feeding mechanism. Thus, the motions of this mechanism are characterized, namely how an elliptic motion of the feed dog is affected by the feeding control mechanism. Therefore, the above mathematical expressions may be a basis for the new design of the feed dog feeding mechanism and may be adapted to analysis. Development of the similar feed dog feeding mechanism can be applied to other type sewing machine.

• 한국전기전자재료학회논문지
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• 제21권2호
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• pp.131-136
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• 2008

The transducer for multi-directionally movable ultrasonic motor having lambda shaped vibrators has been proposed and designed. The two branches cross at a right angle with each other at the tip. FEM analyses of lambda shaped transducer were carried out to find vibration modes for ultrasonic motor. The lambda shaped transducer has one symmetric mode and two anti-symmetric modes. The symmetric mode generates the normal direction motion of the tip. The lateral and vertical direction motion of the tip are excited by two anti-symmetric modes. The normal and lateral direction motions made an lateral elliptic trajectory. And the normal and vertical direction motions made an vertical elliptic trajectory normal to previous one. The transducer with 1 mm in thickness and 25 mm in length has been fabricated and evaluated. The resonance frequencies of the transducer was 32 kHz and 103 kHz. The tangential and vertical vibration displacement of the transducer having the lateral elliptic trajectory were $1.5{\mu}m\;and\;1.1{\mu}m$, respectively at the driving voltage of 100 Vpp and frequency of 32 kHz and 103 kHz. And the tangential and vertical vibration displacement of the transducer having the vertical elliptic trajectory were $0.4{\mu}m\;and\;0.2{\mu}m$, respectively at the same driving condition.

• 천문학논총
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• 제30권2호
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• pp.293-294
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• 2015

This work considers the elliptic restricted three-body problem under effects of radiation of the bigger primary, and an oblate spheroid for the smaller primary to mimic an exoplanetary system with a gas giant planet. Under the influences of both effects we look for the existence of the triangular equilibrium points and the influences of the radiation and oblateness on the locations and motion of the points. We set the system in a normalized rotating coordinate system and derive equations of motion for the third infinitesimal object. Our study shows that the effects modify the equilateral/isosceles triangle shape with respect to the primaries. The triangular points also have non-planar motion with period depending on the value of the planet oblateness.