• Kyungpook Mathematical Journal
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• 제32권1호
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• pp.21-30
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• 1992

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1997년도 춘계학술대회 논문집
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• pp.42-47
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• 1997

In this study, the drawing characteristics of circular drawbead are examined with the plane strain elastic-plastic FE Method by varying the process variables such as friction coefficient, drawbead radius, and closing depth. Numerical analysis are carried out by 2-D elastic-plastic F.E.M. The results are compared with the existing experimental results about the drawing force, the die clamping force, and the strain distribution of upper and lower sheet faces

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집C
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• pp.586-591
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• 2001

In the cold forging, elastic deformation of the die has been investigated to improve the accuracy of cold forged parts with F.E.M analysis using DEFORM, and with experiments using strain gauges. In the experiments, initial billet was selected to easily find the effect of elastic deformation according to the forging modes, extrusion and upsetting type, and only extrusion type. Elastic deformation of the die can be obtained by the signal from the strain gauges and this signal can be amplified by data acquisition system during the process. In the F.E.M analysis, two types of analysis are used to predict elastic strain of the die. To improve an accuracy of forged product and die dimension, this study compared with strain distribution between experiment and F.E.M analysis. As a result, the history of the deformation of the die and elastic recovery of forged product can be obtained by the elastic strain analysis of forged product and die according to the forging modes.

• 한국정밀공학회지
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• 제26권8호
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• pp.96-103
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• 2009

The roll forming process is commonly used for the conventional 'Fe' metal products such as a furniture drawer guide or an up-down slide guide. Recently its applications are variously expanded to the sanitary facilities or electronic devices. It is essentially required the cleanness for the high technology application and any corrosion or rust are not allowed. Therefore, in those applications the stainless steel materials are strongly demanded as the substitution of 'Fe' steel. However the mechanical properties of stainless steel are not suitable for forming process compared with those of 'Fe' steel. Up to now, the conventional F.E.M.(Finite Element Method) has been used to analyze and design the roll forming process. The purpose of this research is to obtain the proper production process and the shape of rolls to manufacture the high precision slide rails made of stainless steel material. The commercial program, SHARPE-RF, is used to analyze the entire roll forming process. The results show that the rolling process and the roll design by F.E.M. are useful from the good agreement between the shapes of products estimated by F.E.M. and those of the actual products.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집A
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• pp.568-572
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• 2001

An industrial vibratory conveyor system is devised for large-scale feeding by the low-power, using natural frequency of the system. The important thing in this system is to determine the natural frequency and to drive by it. The purpose of this study is to build up reliance on the system with changing of element parameters for vibration characteristics of balancing type vibratory conveyor by using F.E.M. modeling. For investigating the natural frequency, modal testing is performed by using impact hammer, accelerometer and LMS/Vibration Analysis System. Experimental results are compared with F.E.M results. The results of the comparisons within the errors of less than 2 percent can verify the reliability of the F.E.M. analysis of the system. Also we can verify that the characteristics of natural frequency have linearly decreased(-6%) as adding the mass($50{\sim}600kg$). We can find that controlling driving frequency is necessary for triggering the natural frequency, but natural frequency is less affected by adding the mass on the balancing weight.

• 한국공작기계학회논문집
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• 제18권2호
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• pp.162-169
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• 2009

This paper describes a study on dynamic characteristics analysis and dynamic compliance evaluation of a 5-axis multi-tasking machine tool of ram-head type. Structural dynamics analysis and evaluation are necessary to machine tool design and development to secure good machine tool performance against tough and harsh machining conditions. In this study, natural frequencies and corresponding vibration modes of the machine tool structure were analyzed by using both F.E.M. modal analysis and impulse hammer test. Furthermore, dynamic compliance of the machine tool was analyzed by using F.E.M. and also measured by using a hydraulic exciter test. Both the theoretical analysis and experimental test results showed good agreement with each other.

• 천문학회보
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• 제40권1호
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• pp.53.3-54
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• 2015

We are developing large arrays of X-ray microcalorimeters for applications in X-ray astronomy. X-ray microcalorimeters can detect the energy of X-rays with extremely high resolution. High-resolution Imaging spectroscopy enabled by these arrays will allow us to study the hot and energetic nature of the Universe through the detection of X-rays from astronomical objects such as neutron stars or black holes. I will introduce the state-of-the-art X-ray microcalorimeters being developed at NASA/GSFC and the future X-ray observatory missions based on microcalorimeters.

• Ocean and Polar Research
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• 제30권3호
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• pp.335-345
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• 2008

In order to study spatial variabilities and major controlling factors, we measured fugacity of $CO_2(fCO_2)$, temperature, salinity and nutrients in surface waters of the North Pacific($7^{\circ}30'{\sim}33^{\circ}15'N$, $123^{\circ}56'E{\sim}164^{\circ}24'W$) between September$\sim$October 2007. The North Pacific and the marginal sea were distinguished by $fCO_2$ distribution as well as unique characteristics of temperature and salinity. There was a distinct diurnal SST variation in the tropical North Pacific area, and surface $fCO_2$ coincidently showed diurnal variation. In the North Pacific area, surface $fCO_2$ was mainly controlled by temperature, while in the marginal sea area it was primarily dependent on alkalinity and dissolved inorganic carbon concentrations. Air-sea $CO_2$ flux showed a large spatial variation, with a range of $-6.10{\sim}5.06\;mmol\;m^{-2}day^{-1}$. The center of subtropical gyre of North Pacific acted as a source of $CO_2(3.09{\pm}0.95\;mmol\;m^{-2}day^{-1})$. Tropical western North Pacific (i.e. the 'warm pool' area and the subtropical western North Pacific) acted as weak sources of $CO_2$($1.07{\pm}1.20\;mmol\;m^{-2}day^{-1}$ and $0.50{\pm}0.53\;mmol\;m^{-2}day^{-1}$, respectively). In the marginal sea, however, the flux was estimated to be $-0.68{\pm}1.17\;mmol\;m^{-2}day^{-1}$, indicating that this area acted as a sink for $CO_2$.

• 대한수학회보
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• 제36권4호
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• pp.671-682
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• 1999

Using a base-point free version of the infinite symmetric product we define a fibrewise infinite symmetric product for any fibration $E\;\longrightarrow\;B$. The construction works for any commutative ring R with unit and is denoted by $R_f(E)\;l\ongrightarrow\;B$. For any pointed space B let $G_I(B)\;\longrightarrow\;B$ be the i-th Ganea fibration. Defining $M_R-cat(B):= inf{i\midR_f(G_i(B))\longrihghtarrow\;B$ admits a section} we obtain an approximation to the Lusternik-Schnirelmann category of B which satisfies .g.a product formula. In particular, if B is a 1-connected rational space of finite rational type, then $M_Q$-cat(B) coincides with the well-known (purely algebraically defined) M-category of B which in fact is equal to cat (B) by a result of K.Hess. All the constructions more generally apply to the Ganea category of maps.

• 한국전자파학회논문지
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• 제14권5호
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• pp.536-541
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• 2003

본 논문에서는 다이아몬드 표면에의 산소흡착을 억제함으로써 양호한 전기적특성을 가지는 다이아몬드 MISFET를 제작하기 위해 초고진공 프로세스(ultrahigh vacuum process)에 의해 A1/Ca $F_2$/diamond MISFET를 제작하였다. 박막반도체 다이아몬드의 표면도전층으로서는 불소종단에 의해 형성되는 표면 도전층을 이용하였다. 초고진공 프로세스에 의해 제작된 A1/Ca $F_2$/diamond MISFET로부터 상용화된 실리콘 MOSFET와 동등한 레벨인~$10^{11}$ /$cm^2$ eV의 저농도의 표면준위밀도가 관측되었고, 유효이동도 $\mu$ $e_{ff}$ 는 이제까지 발표된 박막반도체 다이아몬드 FET중 최고치인 300 $cm^2$/Vs 이었다. 본 논문에서는 또한 초고진공 프로세스에 의해 제작된 Al/Ca $F_2$/diamond MISFET를 이용하여 인버터회로(inverter circuit)를 제작하였으며, 고온고주파 환경에서 양호한 전기적 특성을 관찰하였다. 본 논문의 특징은 초고진공 프로세스에 의해 제작된 불소화 다이아몬드 박막반도체 MISFET에 관한 최초의 보고이며, 또한 다이아몬드 박막반도체 MISFET의 인버터회로(inverter circuit)동작에 관한 최초의 보고이다.다.