• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 춘계학술대회논문집
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• pp.399-406
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• 2001

Thermally induced vibration response of composite thin walled beams is investigated. The thin-walled beam model incorporates a number of nonclassical effects of transverse shear, primary and secondary warping, rotary inertia and anisotropy of constituent materials. Thermally induced vibration response characteristics of a composite thin walled beam exhibiting the circumferentially uniform system(CUS) configuration are exploited in connection with the structural bending-torsion coupling resulting from directional properties of fiber reinforced composite materials and from ply stacking sequence. A coupled thermal structure analysis that includes the effects of structural deformations on heating and temperature gradient is investigated.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 춘계학술대회논문집
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• pp.207-212
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• 2001

In this paper, dynamic stability and vibration characteristics of a flexible shoe in drum brake systems are investigated. The frictional force between the drum and the shoe is assumed as a distributed frictional force, while the shoe is modeled as an elastic beam supported by two translational springs at both ends and elastic foundations. Governing equations of motion are derived by energy expressions, and numerical results are calculated by finite element method. Through the numerical simulation, critical distributed frictional forces are calculated by changing the stiffness of two translational springs and elastic foundation parameters. It is also shown that the beam loses its stability by flutter and divergence depending on the stiffness of elastic supports and elastic foundation parameters. Finally, the time responses of the beam corresponding to their instability types are demonstrated.

• 한국소음진동공학회논문집
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• 제17권11호
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• pp.1119-1126
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• 2007

In this paper, the dynamic stability of a cracked cantilever pipe conveying fluid with tip mass is investigated. The pipe is modelled by the Euler-Bernoulli beam theory in which rotatory inertia and shear deformation effects are ignored. The equation of motion is derived by the energy expressions using extended Hamilton's Principle. The crack section is represented by a local flexibility matrix connecting two undamaged pipe segments. The influence of the crack severity, the position of crack, the mass ratio, and a tip mass on the stability of a cantilever pipe conveying fluid are studied by the numerical method. Besides, the critical flow velocity and the stability maps of the pipe system as a function of mass ratios($\beta$) for the changing each parameter are obtained.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1995년도 춘계학술대회논문집; 전남대학교, 19 May 1995
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• pp.270-275
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• 1995

본 논문에서는 3자유도를 갖는 2차원 강체날개의 플러터 속도를 향상시키는 축차 제어기를 설계하는 기법을 연구하였다. 먼저 2차원 강체날개의 운동방정식을 유도하고 플러터 해석을 수행하였다. 다음 수동계의 플러터 속도를 향상시키는 능동제어기를 설계한 후 제어기의 차수를 축차하는 기법을 적용하여 저차의 능동제어기를 구성하였다. 제어기 축차기법으로는 BACR을 사용하였으며 전차 제어기의 상태변수를 약 80%정도 줄일 수 있다. 축차된 제어기를 사용한 능동시스템과 전차 제어기를 사용한 능동시스템의 제어효과의 차이는 무시 할 수 있을 정도로 매우 작다. 따라서, BACR을 사용하여 얻은 축차된 제어기를 사용하면 상당한 계산량 감소효과와 실시간 단축효과를 얻을 수 있음을 확인하였다. 또한 동일한 돌풍입력에 대한 각각의 능동 시스템의 시간응답도 매우 양호한 결과를 얻을 수 있었으며, 전차 제어기를 사용한 능동시스템의 돌풍응답과 축차된 제어기를 사용한 능동시스템의 돌풍 응답 사이의 차이도 매우 작게 나타났다. 그러므로, 항공기 날개의 능동 플러터억제에는 BACR을 이용하여 설계한 축차된 제어기가 플러터 능동제어에 매우 유용하다고 할 수 있다. 그러나 BACR을 사용하기 위해서는 요구되는 정확도와 계산량에 대한 상호 절충과정이 반드시 필요하다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.1228-1233
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• 2000

A new planform of a wing having two sweep angles is proposed to enhance the aeroelastic stability of a swept-forward wing. The double-swept wing has two sweep angles with inboard wing swept-back and outboard wing swept-forward. Aeroelastic analysis is performed with the finite element method to model wing structure and the doublet point method to predict aerodynamic loads. The sweep angle of the inboard wing is varied in this analysis while the outboard wing is swept forward to a pre-selected amount. The results show that the aeroelastic stability can be drastically enhanced by adjusting the sweep angle of the inboard wing. The effect of the fiber orientation in the double-swept composite wing is studied and the proper ply angle is identified to maximize critical speed.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 춘계학술대회 논문집
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• pp.923-928
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• 2012

In this paper, static and oscillatory instability of a nanotube conveying fluid and modelled as a thin-walled beam is investigated. Analytically nonlocal effect, effects of boundary conditions, transverse shear and rotary inertia are incorporated in this study. The governing equations and the two different boundary conditions are derived through Hamilton's principle. Numerical analysis is performed by using extend Galerkin method which enables us to obtain more exact solutions compared with conventional Galerkin method. Variations of critical flow velocity for different boundary conditions of a nanotube with analytically nonlocal effect, partially nonlocal effect and local effect of a nanotube are investigated and pertinent conclusion is outlined.

• Tribology and Lubricants
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• 제17권1호
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• pp.56-63
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• 2001

The dynamic behavior of rotor-bearing system used in swash plate compressor has been investigated using the combined methodologies of finite elements and transfer matrices. The finite element is formulated including the field element for a shaft section and the point element for swash plate, disk pulley and bearings. The Houbolt method is used to consider the time march for the integration of the system equations. The transient whirl response of rotating shaft supported on roller bearings is obtained, considering compression forces and unbalance forces at swash plate and driving pulley. And, the steady state displacements of the rotor are compared with a variation in unbalance mass. Results show that the loci of rotating shaft considering unbalance forces and external compression forces are more severe in flutter motion than with only unbalance forces.

• Journal of Chest Surgery
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• 제25권6호
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• pp.672-677
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• 1992

This is a clinical review of the results from electric cardioversion and pharmacological therapy used in our hospital for reverting cardiac arrythmia in patients with mitral valve surgery between Jan. 1990 and Jun. 1991. Of 62 evaluated patients, 16 patients had regular sinus rhythm and the other 46 had arrhythmias [42; atrial fibrillation 1; atrial flutter 1; premature ventricular contraction] preoperatively. In 2 of patients with sinus rhythm, atrial fibrillation newly developed after surgery and was converted into sinus rhythm soon by intravenous administration of digoxin. Remaining 14 patient resumed sinus rhythm spontaneously. In patients with preoperative arrythmia, 3 patients reverted into sinus rhythm from atrial fibrillation by electric cardioversion at operative field, 1 patient by lidocain and mexiletine, 4 patients by combined use of digoxin and verapamil, 4 patients by 2 times of oral quinidine and 9 patient by long term use of oral amiodarone. Throughout this consecutive trials of anti-arrhythmic drugs and electric cardioversion, Conversion into normal sinus rhythm occurred in 48% of patients with arrhythmia developed after mitral valve surgery.

• Journal of Chest Surgery
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• 제35권11호
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• pp.817-821
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• 2002

Ebstein기형은 수술적 교정을 위한 여러 가지 변형된 방법들이 소개되고 있지만 수술 후 잔존하는 삼첨판막 역류와 우심부전에 대한 문제는 여전히 남아있다. 본원에서는 심방조동이 동반된 Ebstein기형을 가지고 있는 19세의 남자 환자에 있어서 주름 성형술 없이 간단한 방법으로 삼첨판막 성형술을 시행하였고 양 방향성 상대정맥 -폐동맥 단락술 및 하대정맥 삼첨판 협부의 냉동절제 등을 성공적으로 시행하였기에 문헌고찰과 더불어 증례 보고하는 바이다.

• 한국안전학회지
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• 제13권1호
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• pp.3-12
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• 1998

On the stability of the cantilever beam subjected to a follower force at the free end, the influences of the translational spring and the moment of inertia of a tip mass at the free end have been studied by numerical methods. The centroid of a tip mass is offset from the free end of a Beam and is located along its extended axis to vary the value of moment of inertia of a tip mass. It is proved that as the constants of a spring supporting the free end are augmented, the critical flutter loads of the above system decrease, whereas they increase without a tip mass.