• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1991년도 춘계학술대회 논문집
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• pp.22-31
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• 1991

Machining with boring bars frequently induce chatter vibration because of the low stiffness and damping of cantilever shape of boring bars. To increase stiffness and damping, a carbon fiber epoxy composite boring bar was designed, manufactured and tested. The natural frequency of the carbon fiber epoxy composite boring bar in the free-free end condition was incerased more than 50% over that of the steel boring bar, and the damping of the carbon fiber epoxy composite boring bar was also increased 450%. The fundamental natural frequency of the carbon fiber epoxycomposite boring bar in the cantilever beam condition was found to be increased 20-30% over that of the steel boring bar in overhang length range 140-200mm. In machining S45C tapered workpieces, the limit of the overhang length of the steel boring bar was about 170mm in cutting speed 140m/min.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.859-862
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• 2002

The Core Support Barrel (CSB) is a major component of Reactor Internals, and is designed to support and protect the Reactor Core. In this study, Reactor Core, Core Shroud and CSB were simplified to coaxial cylinders and then the offset of Reactor Core & Core Shroud to the dynamic characteristic of CSB was analyzed. For the beam modes, natural frequencies of the cantilevered cylinder are compared with those of the cantilevered beam. And it was found out that shear modulus must be used correctly to convert the shell model to the equivalent beam model. From the dynamic characteristics of the beam model, it was found out that natural frequencies are proportional to the length of Reactor Core & Core Shroud and inversely proportional to the mass. From the comparison with the dynamic characteristics of a beam model and a lumped-mass model it was found out that the size of lumped-mass must be determined considering both the length and the mass of Reactor Core & Core Shroud.

• 한국의류학회지
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• 제21권8호
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• pp.1376-1386
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• 1997

The purpose of this study is to investigate how one's visual evaluations are affected by variations in internal designs of tailored jackets. Major findings are: 1. Of the 35 pairs of adjectives, the factor analysis singled out the following five major factors (total variance of 55.62%): elegance, maturity, neatness, hard/softness, and evaluation. 2. The image of tailored jackets were found to be significantly affected by the length of its collar: jackets with long collar were perceived elegant, graceful, neat, mature and slim. 3. The number of buttons was also found to have significant impact on the image of tailored jackets: A one-button jacket, single or double, was perceived graceful, mature, formal, neat, natural, brisk, slim and so on. Its image deteriorated as the number of buttons increased. 4. Single jackets were found to be significantly different from Double jacket in their images. The former were perceived elegant, neat, and natural.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.1201-1204
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• 2003

An unconstrained tuning fork with a 3-D model has been numerically analyzed by Finite Element Method(FEM) and Boundary Element Method (BEM). The first three natural frequencies were calculated by the FEM modal analysis. Then the trend of the change of the modal frequencies was examined with the variation of the tuning fork length and width. An formula for the natural frequencies-tuning fork length relationship were derived from the numerical analysis results. Finally the BEM was used fur the sound pressure field calculation from the structural displacement data.

• Structural Engineering and Mechanics
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• 제54권3호
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• pp.419-432
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• 2015

The free vibration of rotating Euler-Bernoulli beams with the thickness and/or width of the cross-section vary linearly along the length is investigated by using the Adomian modified decomposition method (AMDM). Based on the AMDM, the governing differential equation for the rotating tapered beam becomes a recursive algebraic equation. By using the boundary condition equations, the dimensionless natural frequencies and the closed form series solution of the corresponding mode shapes can be easily obtained simultaneously. The computed results for different taper ratios as well as different offset length and rotational speeds are presented in several tables and figures. The accuracy is assured from the convergence and comparison with the previous published results. It is shown that the AMDM provides an accurate and straightforward method of free vibration analysis of rotating tapered beams.

• JSTS:Journal of Semiconductor Technology and Science
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• 제11권2호
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• pp.111-120
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• 2011

A two-dimensional analytical model for deriving the threshold voltage of a short channel fully depleted (FD) cylindrical/surrounding gate MOSFET (CGT/SGT) is suggested. By taking into account the lateral variation of the surface potential, introducing the natural length expression, and using the Bessel functions of the first and the second kinds of order zero, we can derive potentials in the gate oxide layer and the silicon core fully two-dimensionally. Making use of these potentials, the minimum surface potential can be obtained to derive the threshold voltage as a closed-form expression in terms of various device parameters and applied voltages. Obtained results can be used to explain the drain-induced threshold voltage roll-off of a CGT/SGT in a unified manner.

• Animal Systematics, Evolution and Diversity
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• 제25권1호
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• pp.41-47
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• 2009

Two ciliate species of Blepharisma were collected from the riverine wetland and mountain peak soil in Korea, Blepharisma undulans Stein, 1867 and B. steini Kahl, 1932, which are reported for the first time from Korea. The description was based on the observations of live and protargol impregnation specimens. Diagnostics of these species (Blepharisma undulans vs. B. steini) are as follows. Body length/width ratio in vivo about 6/1 vs. 2/1, shaped in spindle vs. pyriform to ellipsoid and colored in pinkish vs. reddish. Macronuclei 2 vs. 1, with 4-9 vs. 4-7 spherical micronuclei. Adoral zone of membranelles extends from anterior end to 1/3 vs. 1/2-2/3 of body length, with 47-56 vs. 33-45 adoral membranelles. The numbers of somatic kineties are 22-27 vs. 18-22.

• Advances in nano research
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• 제7권2호
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• pp.77-88
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• 2019

This paper infer the transient vibration of piezoelectric sandwich nanobeams, In present work, the flexoelectric effect on the mechanical properties of vibration piezoelectric sandwich nanobeam with different boundary conditions is investigated. According to the Nonlocal elasticity theory in nanostructures, the flexoelectricity is believed to be authentic for such size-dependent properties. The governing equations are derived by Hamilton's principle and boundary condition solved by Galerkin-based solution. This research develops a nonlocal flexoelectric sandwich nanobeam supported by Winkler-Pasternak foundation. The results of this work indicate that natural frequencies of a sandwich nanobeam increase by increasing the Winkler and Pasternak elastic constant. Also, increasing the nonlocal parameter at a constant length decreases the natural frequencies. By increasing the length to thickness ratio (L/h) of nanobeam, the nonlocal frequencies reduce.

• Advances in concrete construction
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• 제10권6호
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• pp.499-507
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• 2020

In current study, utilizing the Kelvin's theory with polynomial, exponential and trigonometric volume fraction laws for functionally graded cylindrical shell vibrations. Effects of different parameters for ratios of length- and height-to-radius and angular speed versus fundamental natural frequencies been determined for two categories of cylindrical shells with clamped-free edge condition. By increasing different value of height-to-radius ratio, the resulting backward and forward frequencies increase and frequencies decrease on increasing length-to-radius ratio. Moreover, on increasing the rotating speed, the backward frequencies increases and forward frequencies decreases. The frequencies are same when the cylinder is stationary. The frequencies increases and decreases on changing the constituent materials. The frequency results are verified with the earlier literature for the applicability of present model.

• 식물분류학회지
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• 제31권4호
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• pp.359-373
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• 2001

본 연구에서는 우리나라에 분포하는 애기부들(Typha Augustifolia L.)에 대한 외부형태학적 형질을 조사하여 정확한 실체를 파악하고, 명명상의 혼란을 해소하고자 하였다. 우리나라에 분포하는 애기부들에 대한 학명으로 분류학적 한계의 규명없이 T. angustifolia L. 와 T. angustata Bory et Chaubard가 사용되어 왔다. Typha angustifolia와 T. angustata는 자화의 길이와 소포엽의 길이 비, 소포엽의 길이와 털의 길이 비에 의해 구분되어 왔다. 그러나 이러한 형질은 한 개체에서도 여러 가지 형태적 변이를 나타내고 있으며, 단변량 분석결과 우리나라의 애기부들은 자화와 소포엽의 길이 비 ($1.15{\pm}0.18$)와 소포엽과 털의 길이 비 ($1.00{\pm}0.06$)에서 연속적인 변이 양상을 보이고 있다. 따라서 이러한 형질로는 Typha angustifolia와 T. angustata를 구분할 수 없다. 따라서 T. angustata를 T. angustifolia의 이명으로 처리하였다. 한편, 주성분 분석결과에서 우리나라의 애기부들과 일본, 러시아, 미국등에 분포하는 T. angustifolia와 동일그룹을 형성한다. 따라서 우리나라에 분포하는 애기부들에 대하여 적합한 학명으로는 T. angustifolia가 사용되어져야 할 것으로 보인다.