• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.908-913
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• 2002

An analytical study is presented on the hydroelastic vibration of two rectangular identical plates coupled with a bounded fluid by using the finite Fourier series expansion method. It is observed that the two contrastive modes, the so called the out-of-phase and in-phase modes appear. The proposed analytical method is verified by observing a good agreement to three dimensional finite element analysis results. All natural frequency of the in-phase modes can be predicted well by the combination of the dry beam modes. The theoretical prediction for the out-of-phase mode can be improved by using the polynomial functions satisfying the plate boundary conditions and fluid volume conservation instead of using dry beam modes.

• 대한수학회보
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• 제36권2호
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• pp.395-402
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• 1999

We introduce the notion of strongly k-disk homogeneous apace and establish a characterization theorem. More specifically, we prove that any analytic Riemannian manifold (M,g) of dimension n which is strongly k-disk homogeneous with 2$\leq$k$\leq$n-1 is a space of constant curvature. Its K hler analog is obtained. The total mean curvature homogeneity of geodesic sphere in k-disk is also considered.

• Advances in aircraft and spacecraft science
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• 제10권5호
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• pp.439-455
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• 2023

Free surface fluid oscillation in prolate spheroidal tanks has been investigated analytically in this study. This paper aims is to investigate the sloshing frequencies in spheroidal prolate tanks and compare them with conventional cylindrical and spherical containers to select the best tank geometry for use in space launch vehicles in which the volume of fuel is very high. Based on this, the analytical method (Fourier series expansion) and potential fluid theory in the spheroidal coordinate system are used to extract and analyze the governing differential equations of motion. Then, according to different aspect ratios and other parameters such as filling levels, the fluid sloshing frequencies in the spheroidal prolate tank are determined and evaluated based on various parameters. The natural frequencies obtained for a particular tank are compared with other literature and show a good agreement with these results. In addition, spheroidal prolate tank frequencies have been compared with sloshing frequencies in cylindrical and spherical containers in different modes. Results show that when the prolate spheroidal tank is nearly full and in the worst case when the tank is half full and the free fluid surface is the highest, the prolate spheroidal natural frequencies are higher than of spherical and cylindrical tanks. Therefore, the use of spheroidal tanks in heavy space launch vehicles, in addition to the optimal use of placement space, significantly reduces the destructive effects of sloshing.

• 한국항해항만학회지
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• 제35권4호
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• pp.343-349
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• 2011

The forecasting of container volume which is the basis of port logistics facilities expansion has a great influence on development of an port. Based on this importance, various previous studies have presented methodology on container volume forecasting. The results of many previous studies pointed out the limitations of future forecasting based on past container volume and emphasized that more various factors should be considered to compensate this. Taking notice of this point, this study forecasted future container volume by using ARIMA model, time series analysis and System Dynamics (SD) method, a dynamic analysis technique and performed the comparative review with the forecast of the Ministry of Land, Transport and Maritime affairs. Recently with rapid changes in economic and social environment, the non-linear change tendency for forecasting container traffic is presented as a new alternative to the country.

• 한국재료학회지
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• 제11권10호
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• pp.863-868
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• 2001

The present study was carried out to investigate the effect of MA processing variables on the microstructural properties of composite powders and the coefficient of thermal expansion of pulse electric current sintered AlN-Cu powder compacts. The AlN-Cu powders had a size of less than 15 $\mu\textrm{m}$ with 25 nm size of copper crystallite after MA 32 hours. The finely distributed AlN-Cu powder compacts were completely achieved after PECS. The residual oxygen was considerably removed after hydrogen reduction treatment. The residual carbon was completely removed to 97%. The CTE of AlN-Cu powder compacts showed a good consistency with Kingery-Tuner model when the volume fraction of copper was less than 60%. When it was more than 60%, the CTE had a good agreement with Series model.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.80-82
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• 2004

The single phase switched reluctance motor(SRM) is more simpler and robust in the structure than poly phase SRM. It has the merits that it reduces the switching elements and the energy density per volume is very high. Recently, it has been researched and developed in various types and starting method due to the technique of power electronics and the computer added design. This paper presents a analytical representation of the phase inductance of a single phase SRM, as function of position and current, taking into account the non-linearity of the magnetic circuit. the method is based on Fourier series expansion. Analytical expressions for the calculation of instantaneous phase inductance, flux linkage, coenergy and electromagnetic torque as a function of rotor position and winding currents are derived.

• 한국수자원학회논문집
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• 제33권1호
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• pp.31-38
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• 2000

수문변량 사이의 관계는 대부분 비선형 관계를 보이고 있다. 일반적으로 이런 비선형 관계는 어떤 선행하는 명백한 하나의 함수적인 형태로 표현할 수 없는 것이 일반적이다. 본 논문에서는, 비매개변수적 다변량 회귀분석 방법을 지역적으로 가중된 다항식을 이용하여 비선형 예상 함수를 추정하였다. 지역적으로 가중된 다항식은 추정치 각 점에서의 인접한 이웃자료를 가지고 목적 함수를 테일러 급수 확장을 통하여 고려하였다. 이런 비매개변수적 회귀분석을 실용성을 Great Salt Lake의 격주 체적자료에 대한 단기간 예측을 통하여 보여주었다.

• Journal of Magnetics
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• 제6권2호
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• pp.57-60
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• 2001

Mechanically alloyed $TbCu_7 -type \;Sm_{12.5}Fe_{87.5-x}Ti_x$(x=0, 2.5, 5, 7.5),and their nitrides have been studied systematically by X-ray diffraction, A.C. initial susceptibility, and pulsed magnetization measurement. In this series, the volume expansion by nitriding is 5.6%~7.3%, and the increment of the Curie temperature is in the range of 21$0^{\circ}C$~35$0^{\circ}C$. With increasing Ti content, the remanence decreases linearly due to the substitution of non-magnetic Ti, and the coercivity decreases rapidly from 34.6 kA/cm (43.5 kOe) for $\chi$=0 to 14.3 kA/cm (18 kOe) for $\chi$=7.5. In the $Sm_{12.5}Fe_{87.5-x}Ti_xN_y$ series, the best magnetic properties were obtained from .7Ti7Ny series, the best magnetic properties were obtained from $Sm_{12.5}Fe_{87.5}N_y$($\chi$=0) with $_iH_c$=34.6 kA/cm (43.5 kOe), $B_r=0.75 \;T, \;and (BH)_{max}=113.8 kJ/m^3$(10.9 MGOe).

• 한국전산유체공학회지
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• 제11권4호
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• pp.39-47
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• 2006

In this paper, the authors developed a multidimensional interpolation method inside a finite volume cell in the computation of high-order accurate numerical flux such as the fifth order WEND (weighted essentially non-oscillatory) scheme. This numerical method starts from a simple Taylor series expansion in a proper spatial order of accuracy, and the WEND filter is used for the reconstruction of sharp nonlinear waves like shocks in the compressible flow. Two kinds of interpolations are developed: one is for the cell-averaged values of conservative variables divided in one mother cell (Type 1), and the other is for the vertex values in the individual cells (Type 2). The result of the present study can be directly used to the cell refinement as well as the convective flux between finer and coarser cells in the Cartesian adaptive grid system (Type 1) and to the post-processing as well as the viscous flux in the Navier-Stokes equations on any types of structured and unstructured grids (Type 2).

• 무역상무연구
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• 제75권
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• pp.95-116
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• 2017

The global financial crisis has slowed overall growth in the global economy. In addition, uncertainty is increasing in the world economy due to the Trade protectionism, sluggish world trade, and a rise in the rate of interest caused by expansion of fiscal spending by major countries. In this study, we analyzed various factors affecting the container import and export volume, which has a high correlation with export and import of commodities in international trade. In particular, we will examine how exchange rate fluctuations and domestic and overseas economic conditions affect container imports and exports. For the empirical analysis, monthly time series data were used from January 2000 to January 2017. We use the Error Correction Model (VECM) for the empirical analysis and the GARCH model for the exchange rate fluctuation. As a result, container export and import volume had a negative relationship with exchange rate and exchange rate volatility, which had a positive effect on domestic and international economic conditions. However, the effects are different before and after the financial crisis.