• 조명전기설비학회논문지
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• 제14권3호
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• pp.88-96
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• 2000

순시전력이론은 수학적으로 이해가 용이하며, PWM 전력변환기를 $\alpha$-$\beta$ 정지 좌표에서 비교적 쉽게 제어할 수 있기 때문에 많은 연구가 되어 오고 있다. 그런데 순시진력이론은 보상기준전류 계산과정에 없어서 많은 전류 성분과 전력성분이 얻어지며 이는 순시전력이론의 불리적인 해석에 영향을 주고 있다. 특히 순시전력이론올 처음 접하는 초보 연구자들은 이와 같은 순시전력의 직류 및 교류성분 그리고 순시전류획 $\alpha$-$\beta$정분의 표준 파형에 대한 정보가 부족하기 때문에 각 성분들의 계산이 맞는지 확인하기 어려웠다. 따라서 본 연구에서는 MATLAB/SIMULINK에 의하여 순시전력이론의 전류성분파 전력성분올 파형과 $\alpha$-$\beta$공간궤적으로 나타내어 초보 연구자들의 이해를 돕도록 하였다. 또한 순시전력 성분 보상애 따른 보상기준 전류 파형이 비선형 부하 계통의 전원전류 파형에 미치는 영향을 쉽게 파악할 수 있도록 하였다.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제5권2호
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• pp.101-115
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• 2001

Recent theoretical analysis of numerical methods for solving nonlinear systems of equations is represented by alpha theory of Newton method developed Smale et al. The theory was extended to Secant method by providing convergence conditions by Yakoubsohn which the Secant method is treated as an operator defined for analytical functions. We use Secant methods as an iterative scheme with approximations, which results in new convergence conditions. We compare the two conditions and show that the new conditions represent the features of Secant method in a more precise way.

• 대한화학회지
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• 제57권6호
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• pp.684-690
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• 2013

Since a glycerol molecule has three active sites, two ${\alpha}$ and one ${\beta}$ hydroxyl groups; it undergoes condensation by releasing water molecules to produce linear, nonlinear and heterocyclic oligomers. The Gibbs free energy (G), enthalpy (H) and internal energy (E) of 7 diglycerol, 15 triglycerol and 23 tetraglycerol isomers were calculated at B3LYP level of theory using 6-311++G(d, p) basis set, in both gas and aqueous phases. Linear oligomers, ${\alpha}{\alpha}$-diglycerol, ${\alpha}{\alpha}$, ${\alpha}{\alpha}$-triglycerol and ${\alpha}{\alpha}$, ${\alpha}{\alpha}$, ${\alpha}{\alpha}$-tetraglycerol, were found to be the most stable oligomers in aqueous phase. It was found that the stability of cyclic oligomers decreases as the size of their rings increases. Cyclic oligomers are produced by dehydration of the acyclic ones which is an endothermic reaction while its ${\Delta}G$ is negative. The dehydration reaction is less endothermic in aqueous phase.

• 폴리머
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• 제38권4호
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• pp.411-416
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• 2014

극성을 띠고있어 응집되는 성향이 카본블랙에 비해 강한 실리카의 분산도는 고무 복합소재의 물성을 좌우하는 중요한 요소이다. Wolff는 입자간 상호계수(${\alpha}_F$)를 도입하여 충전제간의 구조발달을 최초로 표현하였다. 하지만, 양기능성 실란의 도입에 따라 형성되는 3차원 구조발달은 표현할 수 없었다. 후에 이를 보완하기 위하여 Wolff의 표현은 복합소재 내 ${\alpha}_F$를 포함하는 구조발달 상호계수 ${\alpha}_C$로 확장되어 표현되었지만, 실험적으로 이 표현을 증명한 연구는 없었다. 이 논문은 구조발달 상호계수인 ${\alpha}_C$를 ${\alpha}_F$(실리카-실리카간 구조발달 상호계수), ${\alpha}_{FP}$(실리카-실란-고무간 구조발달 상호계수), ${\alpha}_P$(고무-고무간 구조발달 상호계수)로 고려하여 단기능성 및 양기능성 실란으로 처리된 실리카가 함유된 복합소재를 실험에 의해 최초로 표현하였다. 구조가 다른 실란들(PTES, OTES, TESPD, TESPT)을 이용하여 구조발달 상호계수 ${\alpha}_C$를 구성하는 ${\alpha}_F$, ${\alpha}_{FP}$, ${\alpha}_P$의 수치들을 측정하고 계산하였다. TESPT가 첨가된 복합소재의 ${\alpha}_C$의 값은 1.64이며, 이를 구성하고 있는 ${\alpha}_F$, ${\alpha}_{FP}$, ${\alpha}_P$는 각각 0.99, 0.31, 0.34로 나타났다.

• 대한수학회보
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• 제23권2호
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• pp.167-170
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• 1986

Let M be a von Neumann algebra and .alpha., .betha. be *-automorphisms of M satisfying the operator equation .alpha.+.alpha.$^{-1}$ =.betha.+.betha.$^{-1}$ This operator equation has been extensively studied and many important decomposition theorems have been obtained by several authors (for instance see [4], [5], [2], [1]). Originally, this operator equation arose in the paper of Van Daele on the new approach of the Tomita-Takesaki theory in the case of modular operators ([7]). In the case of one-parameter automorphism groups, this equation has produced a bounded and completely positive map which can play a role similar to the infinitesimal generator (for details see [6] and [1]). A recent and one of the most important applications of this equation has been in developing an anglogue of the Tomita-Takesaki theory for Jordan algebras by Haagerup [3]. One general result of this theory is the following.

• 태양에너지
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• 제17권1호
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• pp.35-46
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• 1997

In this study comparison of experiment results with the computed results of linear theory and nonlinear theory using singularity method was obtainable. Specially singularity points like sources and vortexes on hydrofoil and freestreamline were distributed to analyze two dimensional flow field of supercavitating cascade using nonlinear theory, and governing equations of flow field were derived and hydraulic characteristics of cascade were calculated by numerical analysis of the governing equations. The results compared linear theory and nonlinear theory with the experiment results of the study are as follows: The tolerances of nonlinear theory were larger than those of linear theory in case of ${\alpha}<10^{\circ}$. Moreover the computational range of attack angles could be expanded from ${\alpha}=10^{\circ}$ to ${\alpha}=25^{\circ}$, the flow field of supercavitating cascade could be analyzed in the condition which the wake thickness and the length of cavity are a variable. The shapes of cavity were changed sensitively according to various variable such as attack angles, pitches and wake thickness, and the pressure distribution of hydrofoil surface was identical almost disregarding wake thickness but changed largely according to attack angle and the length of cavity. Lift coefficient and drag coefficient were reduced according to increasing of wake thickness but the influences of wake thickness were very little in the situation of small pitch and long cavity.

• Nuclear Engineering and Technology
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• 제48권2호
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• pp.482-494
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• 2016

The Feshbache-Kermane-Koonin (FKK) multi-step direct (MSD) theory of pre-equilibrium reactions has been used to compute the single-step cross-sections for some (p,${\alpha}$) reactions using the knock-on and pick-up reaction mechanisms at two incident proton energies. For the knock-on mechanism, the reaction was assumed to have taken place by the direct ejection of a preformed alpha cluster in a shell-model state of the target. But the reaction was assumed to have taken place by the pick-up of a preformed triton cluster (also bound in a shell-model state of the target core) by the incident proton for the pick-up mechanism. The Yukawa forms of potential were used for the proton-alpha (for the knock-on process) and proton-triton (for the pick-up process) interaction and several parameter sets for the proton and alpha-particle optical potentials. The calculated cross-sections for both mechanisms gave satisfactory fits to the experimental data. Furthermore, it has been shown that some combinations of the calculated distorted wave Born approximation cross-sections for the two reaction mechanisms in the FKK MSD theory are able to give better fits to the experimental data, especially in terms of range of agreement. In addition, the theory has been observed to be valid over a wider range of energy.

• 대한수학회논문집
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• 제10권3호
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• pp.699-705
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• 1995

We first generalize the Volodin space which Volodin constructed in order to define a new algebraic K-theory. We investigate the topological (homotopy) properties of the general Volodin space. We also provide a theorem which seems to be useful in pure homotopy theory. We prove that $V(*_\alpha G_\alpha, {G_\alpha})$ is simply connected.

• Water Engineering Research
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• 제1권4호
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• pp.293-298
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• 2000

Optimal values of $\alpha$ characterizing the linear dispersion property in the modified Boussinesq equations are determined by minimizing the combined relative errors of the phase and group velocities. The value of $\alpha$ is fixed in previous studies, whereas it is varying in the present study. The phase and group velocities are calculated by using variable $\alpha$ and compared to those of the linear Stokes wave theory and previous studies. It is found that the present study produces the best match to the linear Stokes theory.

• 터널과지하공간
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• 제7권4호
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• pp.334-340
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• 1997

Alpha center theory which was first proposed by Stefanescu has been proved to be effective for the detection of the location of the conductive orebody. A numerical forward modeling was conducted to verify the effectiveness of this method. Field works were carried out along the three profiles in two different areas for the purpose of finding fractured zone which might be accompanied with the presence of the groundwater. And the results were modeled by alpha center method, which was later testified by wellproven 2-dimensional finite difference inversion scheme. Field data could be successfully modeled with this alpha center algorithm, especially for the smooth-varying resistivity models. For the abrupt change of the resistivity values, the alpha center coefficients have a tendency to be negative to simulate the steep resistivity gradients. This method is quite simple and easy for the future applications. The numerical calculation can be performed very quickly with the personal computers.