• 한국강구조학회 논문집
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• 제16권1호통권68호
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• pp.81-89
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• 2004

구조물과 같은 아치의 진동해석은 많은 산업분야에서 다양하게 적용되기 때문에 공학적 문제에 중요한 주제이다. 특히 변화하는 단면형상을 가지는 아치는 질량이나 강도를 최적화 하거나 특별한 구조물이나 요구조건들을 만족하기 위해서 폭넓게 사용되어 진다. 최근에는 일반화 미분구적법(GDQM)이나 미분변환법(DTM)은 각각 Shu와 Zou에 의해서 제안이 되었다. 연구에서는 변화하는 단면형상을 가지는 아치의 진동해석이 일반화 미분구적법과 미분변환법을 적용하였다. 변화하는 단면형상을 가지는 아치에 대하여 지배방정식이 유도되어졌으며, 미분변환과 일반화 미분구적법의 개념이 간단히 소개되었다. 변화하는 단면형상을 가지는 아치의 무차원화된 고유진동수가 다양한 경계조건에 대해서 구해졌으며, 이러한 방법들에 의해서 얻어지는 결과들은 선행연구와 비교 되어졌다. 일반화 미분구적법과 미분변환법은 변화하는 단면형상을 가지는 아치의 진동문제를 해석함에 있어서 빠른 수렴, 정확도, 효율성, 유효성을 보인다.

• 대한기계학회논문집
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• 제11권1호
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• pp.132-144
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• 1987

본 논문에서는 Isida의 이론해석 방법을 참고로 하여 유한한한 폭을 갖는 두 께가 변화하는 판재에서의 응력확대계수를 2차원 이론해석한 것이다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 춘계학술대회논문집
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• pp.877-882
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• 2005

Dynamic stability of an axially accelerating beam stucture is investigated in this paper. The equations of motion of a fixed-free beam are derived using the hybrid deformation variable method and the assumed mode method. Unstable regions due to periodical acceleration are obtained by using the Floquet's theory. Stability diagrams are presented to illustrate the influence of the dimensionless acceleration, amplitude, and frequency. Also, buckling occurs when the acceleration exceeds a certain value. It is found that relatively targe unstable regions exist around the first bending natural frequency, twice the first bending natural frequency, and twice the second bending natural frequency. The validity of the stability diagram is confirmed by direct numerical integration of the equations of motion.

• 한국정밀공학회지
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• 제20권5호
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• pp.39-39
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• 2003

As the design rules in semiconductor manufacturing process become more and more stringent, the higher degree of planarization of device surface is required for a following lithography process. Also, it is great challenge for chemical mechanical polishing to achieve global planarization of 12” wafer or beyond. To meet such requirements, it is essential to understand the CMP equipment and process itself. In this paper, authors suggest the velocity distribution on the wafer, direction of friction force and the uniformity of velocity distribution of conventional rotary CMP equipment in an analytical method for an intuitive understanding of variation of kinematic variables. To this end, a novel dimensionless variable defined as “kinematic number” is derived. Also, it is shown that the kinematic number could consistently express the velocity distribution and other kinematic characteristics of rotary CMP equipment.

• 한국정밀공학회지
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• 제20권5호
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• pp.29-38
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• 2003

As the design rules in semiconductor manufacturing process become more and more stringent, the higher degree of planarization of device surface is required for a following lithography process. Also, it is great challenge for chemical mechanical polishing to achieve global planarization of 12” wafer or beyond. To meet such requirements, it is essential to understand the CMP equipment and process itself. In this paper, authors suggest the velocity distribution on the wafer, direction of friction force and the uniformity of velocity distribution of conventional rotary CMP equipment in an analytical method for an intuitive understanding of variation of kinematic variables. To this end, a novel dimensionless variable defined as “kinematic number” is derived. Also, it is shown that the kinematic number could consistently express the velocity distribution and other kinematic characteristics of rotary CMP equipment.

• 설비공학논문집
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• 제3권5호
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• pp.365-375
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• 1991

Confined natural convection due to lateral temperature difference in rectangular enclosures was studied numerically and experimentally for the insulated and the constant temperature enclosures. In the case of insulated enclosure, the flow pattern and heat transfer modes are rather simple depending mainly upon Rayleigh number. In the case of isothermal enclosure, however, the phenomena of flow and heat transfer are somewhat complex and interesting due to the stable thermal gradients and various circumstances resulted from four wall temperature conditions. As a dimensionless variable, to describe properly the flow and heat transfer phenomena in the isothermal enclosure, temperature difference ratio ${\Delta}T_v/{\Delta}T_H$ is newly introduced and this parameter seems to be appropriate in the analysis of results on the effect of stabilizing thermal gradient.

• 동력기계공학회지
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• 제14권4호
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• pp.17-22
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• 2010

본 연구는 구의 과도 열전도에 의한 열손실을 계산하는 데 있어, 외부의 경계조건인 대류의 조건에 해당하는 상황을 상수 및 변수로 가정하였을 경우의 열전달문제를 해석한 것이다. 이 문제를 해결하기 위해 집중열용량법을 사용하고 있으며, 대류열전달계수의 값이 온도의 함수로 변한다고 가정하여 계산하였다. 계산을 수행한 결과 대류경계조건의 값을 상수로 가정한 경우가 열손실이 높이 평가된다는 것을 알았고, 이러한 경향을 상관식으로 정리하였다.

• 수산해양기술연구
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• 제22권1호
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• pp.49-57
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• 1986

The vibrations problem of thin orthotropic skew plates of linearly varying thickness is analyzed using the small deflection theory of plates. Using dimensionless oblique coordinates, the deflection surface can be expressed as a polyonmial series satisfying the boundary conditions. For orthotropic plates which is clamped on all the four edges, numerical results for the first two natural frequencies are presented for various combinations of aspect ratio, skew angle and taper parameter. The properties of material used are one directional glass fibre reinforced plastic GFRP. The results obtained may be summarised as follows: 1. In case of the first mode vibration of plates with increase in the skew angle, the natural frequencies of plates decrease. 2. As the aspect ratio decrease, the natural frequencies of plates decrease. 3. For the identical skew angle, natural frequencies of plates increase with the taper parameter of thickness.

• Tribology and Lubricants
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• 제28권6호
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• pp.303-314
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• 2012

In this research, spool valves with spiral grooves are suggested and their lubrication characteristics are investigated by numerical analysis. The three-dimensional flow field is obtained by solving the Navier-Stokes equations in dimensionless form, so that the performance variables such as lateral force, friction force and volume flow rate are determined. Also, the lubrication characteristics of spool valves with spiral grooves are compared with those with typical grooves under variable working conditions. It is shown that spool valves with spiral grooves can get better performance in aspect of mitigation of uneven pressure distribution surrounding spool. Moreover, it is found that the minimum distance between spool edges and grooves, the type of spiral groove, and the groove angle have noticeable effect on the lubrication characteristics.

• 한국소음진동공학회논문집
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• 제20권11호
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• pp.1052-1057
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• 2010

Dynamic stability of rotating blade considering gravity effect is investigated in this paper. Equations of motion for the beam is derived by employing hybrid deformation variable method and transformed into dimensionless form. The present modeling method is verified by RecurDyn. Stability diagrams are presented to show the influence of the configuration of the beam and angular velocity on the dynamic stability by applying Floquet's theory. Since the natural frequencies are varied when the blade has rotating motion, it is found that relatively large unstable regions exist approximately 1.1 times as high as the first bending natural frequency and half of the sum of first and second bending natural frequency.