• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.803-808
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• 2000

This thesis studied whether friction welding of SPSS, localized torsion bar material could be accomplished or not. And then optimum welding conditions were examined and leaded through tensile, impact, torsion and hardness test after postweld heat treatment of the actual field condition. Obtained results were as follows; Linear relationship was existed between heating time and total upset, and a quadratic equation model could be made between tensile strength and heating time. Optimum welding conditions with fine structure were as follows in case total upset(U)=8.5mm; the number of rotations(n)=2,000 rpm, heating pressure($p_1$)=80MPa, upset pressure($p_2$)=200MPa, heating time($t_1$)=4sec, upset time($t_2$)=3 sec.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2000년도 춘계학술대회논문집 - 한국공작기계학회
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• pp.66-72
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• 2000

Commercial eddy current dynamometers control the torque of ratating body (poer supply machine) with the field coil current being operated as a braking force. In this paper, we studied about the relation between the field coil current and the torque load of eddy current dynamometer. By the torque measuring analysis of eddy current dynamometer, it is linear relation between the brake force measured from the torque meter (e.g. load cell, strain gage or spring balance etc.) which is installed at the case of dynamometer and the multiply of shaft rpm by the square of field coil current (N$\times$Ia2). To prove the relation, it was experimented and showed that the torque operated by the rotating body can be measured with the shaft rpm and the field coil current of eddy current dynamometer. This result shows a possibility that eddy current dynamometer can measures the torque of rotating body without special torque measuring devices.

• 대한기계학회논문집A
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• 제21권2호
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• pp.337-345
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• 1997

An analysis is presented for the response of a beam constrained by a nonlinear spring to a harmonic excitation. The system is governed by a linear partial differential equation with a nonlinear boundary condition. The method of multiple scales is used to reduce the nonlinear boundary value problem to a system of autonomous ordinary differential equations of the amplitudes and phases. The case of the third-order subharmonic resonance is considered in this study. The autonomous system is used to determine the steady-state responses and their stability.

• 물과 미래
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• 제18권1호
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• pp.67-73
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• 1985

금강 감조구간의 조석전파현상을 장파, 중력파공식의 수치적분에 의한 통상적인 방법을 이용하여 조사하였다. 이용된 역학방정식은 비선형항을 포함하여 천해조를 산정할 수 있도록 하였다. 수립된 모델은 평균대, 중, 소조시의 감조구간의 조석전파를 산정하는데 이용되었으며 또한 상류홍수유출과 하구조석의 상호작용에 의한 감조구간의 수립분포를 산정하는데도 초기적용되었다. 이 연구의 목적은 하구의 체절공사가 시작되기 전의 금강감조구간의 조석역학을 조사하는데 있다.

• 한국정밀공학회지
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• 제25권4호
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• pp.100-107
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• 2008

Bellows is an important component in Joule-Thomson cryocooler, which minimize the excessive flow of the cryogenic gas. The bellows is made of Monel 400 and its geometry is an axial symmetric shell. During cool-down process, the pressure and volume within bellows must be satisfied with Benedict-Webb-Rubin state equation. Moreover, Poisson's ratio of Monel 400 is nearly constants, but its Young's modulus varies for a drop in temperature. Under these conditions, bellows contracts in the axial direction like a spring. To evaluate deformation of bellows at cryogenic temperature, the numerical calculation of the volume within bellows and finite element analysis are iteratively used in this research. the numerical results show that deformation of the bellows is approximately linear for change of temperature.

• KSTLE International Journal
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• 제1권1호
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• pp.43-47
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• 2000

Oil seals will experience a small amplitude dynamic excitation due to the shaft eccentricity as well as out-of-roundness of the shaft. The direct integration method is selected to analyze the time domain response of the seal lip-shaft contact. The physical properties of rubber seal materials are experimentally analyzed. Effects of both frequency and temperature on the material stiffness behavior are investigated for the linear viscoelastic materials of the seal. Using the nonlinear transient model, a finite element analysis of the lip-shaft contact behaviors under dynamic conditions is presented as a function of the shaft eccentricity, the shaft interference and the garter spring stiffness. The FEM results based on the experimental data indicate that the increased rotating speed may produce the separation conditions. These results will be very useful in predicting the leakage of oil seals under dynamic conditions.

• 한국조리학회지
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• 제23권4호
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• pp.105-115
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• 2017

Water is an essential ingredient to brew coffee. Mineral contents in the water can affect both water quality and taste quality of coffee. The effects of minerals in the water on sensory characteristics of coffee were investigated in different water samples (A: Arisu, B: Claris, C: Spring water, D: Samdasoo, E: Evian, Distilled water as control). Based on the results of quantitative descriptive analysis (QDA), there were statistically significant (p<0.01) in flavor, acidity, bitterness, sweetness, body and aftertaste according to different water samples used to brew coffee. The canonical correlation analysis of minerals (Ca, Mg, Na, K) and taste (acidity, bitterness, sweetness) indicated that there were highly correlated in the relationship between bitterness and Mg content. A strong negative relationship was shown between bitterness and acidity, sweetness. A result of preference test using hedonic scale showed an inverse linear relationship between taste quality and total mineral contents.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.87-89
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• 2001

The unbalanced reciprocation force due to armature reaction field decreases the advantage of moving coil linear motor, such as a high degree of linearity and controllability in the force and motion control. This paper firstly describes the coil inductance, and the unbalanced force. Secondly, the dynamic simulation algorithm considering the armature reaction effect and variable inductance is proposed. Thirdly, the control algorithm is proposed to reciprocate a load without mechanical spring at the required stroke and position. Finally, the validity of the proposed algorithm is confirmed by experiments.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2004년도 유체기계 연구개발 발표회 논문집
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• pp.98-103
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• 2004

This paper presents modeling and simulation of the bump foil bearings with consideration of the elastic behavior of the foil and gas compressibility. Heshmat had originally introduced the simple compliance model to estimate the EHL(elasto-hydrodynamic lubrication) performance. But this approach can not consider the deflection of top foil at the edge of bearing, so model is insufficient to analyze in case that the eccentricity ratio is greater than I. So the top foil is considered as a simple beam model supported by linear spring elements, and the bump foil deflection can be simple compliance model. The EHL calculations are performed for convention rigid type, classical foil type, variable pitch type and double bump type toil bearings. This paper presents that 2nd or 3rd generation bearings have excellent performance in every speeds.

• Structural Engineering and Mechanics
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• 제35권6호
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• pp.699-715
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• 2010

This paper investigates the structural responses of axially restrained steel beams under fire conditions by a nonlinear finite element method. The axial restraint is represented by a linear elastic spring. Different parameters which include beam slenderness ratio, external load level and axial restraint ratio are investigated. The process of forming a mid-span plastic hinge at the mid-span under a rising temperature is studied. In line with forming a fully plastic hinge at mid-span, the response of a restrained beam under rising temperature can be divided into three stages, viz. no plastic hinge, hinge forming and rotating, and catenary action stage. During catenary action stage, the axial restraint pulls the heated beam and prevents it from failing. This study introduces definitions of beam limiting temperature $T_{lim}$, catenary temperature $T_{ctn}$ and warning time $t_{wn}$. Influences of slenderness ratio, load level and axial restraint ratio on $T_{lim}$, $T_{ctn}$ and $t_{wn}$ are examined.