• Bulletin of the Society of Naval Architects of Korea
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• v.16 no.3
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• pp.1-8
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• 1979

Various approaches to the analysis of stiffened plating in ship structures have been proposed by a number of researchers. Among them, the finite element method is known to be the most powerful method. However, for many parts of ship's structure having simple geometry and boundary conditions, the F.E.M. is often extravagant and unnecessary. In this paper, the authors have attempted to introduce the finite strip method which was proposed by Y.K. Cheung to avoid the difficulties involved in F.E.M. The results of calculations on the displacements and stresses in various plates with or without stiffeners were satisfactory, which shows the F.S.M. is useful for structural analysis of ship's plating.

• Journal of KSNVE
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• v.4 no.4
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• pp.443-449
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• 1994

In the analysis of circular cylindrical shell's vibration and sound radiation, there are numerical and analytical methods. Numerical methods such as F.E.M and B.E.M, have the limit of frequency range. Analytical method can be applied to the circular cylindrical shell from low frequency to high frequency. In this paper, we use the analytical method for shell, and numerical method, F.D.M, for fluid. We also use the method using transfer matrix and eigenanalysis of transfer matrix which can therefore calculate the rotational d.o.f that is very imkportant in synthesis with inner structure. Inner structure has much effect on the submerged circular cylindrical shell vibration and sound rediation. Results for the immersed circular cylindrical shell vibration and sound radiation are compared with the analytic solutions.

• Journal of the Korean Mathematical Society
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• v.51 no.5
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• pp.881-895
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• 2014

In a recent paper [10] we introduced the notion of Levi harmonic map f from an almost contact semi-Riemannian manifold (M, ${\varphi}$, ${\xi}$, ${\eta}$, g) into a semi-Riemannian manifold $M^{\prime}$. In particular, we compute the tension field ${\tau}_H(f)$ for a CR map f between two almost contact semi-Riemannian manifolds satisfying the so-called ${\varphi}$-condition, where $H=Ker({\eta})$ is the Levi distribution. In the present paper we show that the condition (A) of Rawnsley [17] is related to the ${\varphi}$-condition. Then, we compute the tension field ${\tau}_H(f)$ for a CR map between two arbitrary almost contact semi-Riemannian manifolds, and we study the concept of Levi pluriharmonicity. Moreover, we study the harmonicity on quasicosymplectic manifolds.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.1394-1399
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• 2001

The purpose of this paper is that investigates the dynamic behavior characteristic of W.T.S(Wind Turbine System) and carries out the evaluation analysis during operating W.T.S. To investigate the dynamic behavior characteristic of W.T.S. the experiments to measure vibration of the blade from the attached accelerometer on the flap and edge section of the blade that is one of the most important elements of dynamic characteristic of W.T.S are performed. Natural frequency and mode shape are calculated with commercial program (STAR MODAL) using the measured vibration acceleration that receives the signal with F.F.T Analyzer from the accelerometer. For validation of these experiments. the finite element analysis is performed with commercial F.E.M Program (ANSYS) on the basis of the natural frequency and mode shape. The results indicate that experimental values have good agreements with the finite element analysis.

• Development and Reproduction
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• v.2 no.2
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• pp.179-187
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• 1998

The effects of prostaglandins in hatching and implantation have been studied but the results were various, and those are not well known by the embryonic stage. The present study examined the effects of prostaglandin $E_2$(PG $E_2$) and prostaglandin $F_2$$_{\alpha}$ (PG $F_2$$_{\alpha}$) on the expansion and hatching of mouse embryos by embryonic stage. Also we tried to measure the concentration of prostaglandins of morula, expanded, and hatching embryos. In early morula stage embryos, high concentration of PG $E_2$(>100$\mu$M) showed cytotoxicity but PG $F_2$$_{\alpha}$ did not. The hatching was inhibited all groups but not gave negative effects on expansion. In 84 hr and 96 hr stage embryos, the hatching rate was decreased at all treatment groups but not inhibited the expansion. When combine prostaglandin with indomethacin, the hatching rate was increased significantly compared to the prostaglandin-treated groups, and as lower and lower the PG $E_2$ concentration, the hatching rate increased to the control level. The embryonic synthesis of PG $E_2$ increased dramatically but that of PG $F_2$$_{\alpha}$ increased gradually. PG $E_2$ showed cytotoxicity at early stage embryos much than late stage embryos, but PG $F_2$$_{\alpha}$ did not. Hatching was inhibited by the high PG $F_2$$_{\alpha}$ concentration. It is suggested that the inhibition of hatching might be at resulted from cytotoxicity of PG $E_2$ on embryo. However, it is thought that the mechanisms of inhibition of hatching are different between PG $E_2$ and PG $F_2$$_{\alpha}$. In conclusion, it can be suggested that PG $E_2$ and PG $F_2$$_{\alpha}$ concerned with the expansion and hatching, and their effects on hatching were different by the embryonic stage.$/ concerned with the expansion and hatching, and their effects on hatching were different by the embryonic stage.

• Bulletin of the Korean Mathematical Society
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• v.20 no.1
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• pp.31-36
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• 1983

Let R be a commutative ring with 1, and A a unitary commutative R-algebra. By a derivation module of A, we mean a pair (M, d), where M is an A-module and d: A.rarw.M and R-derivation, i.e., d is an R-linear mapping such that d(ab)=a)db)+b(da). A derivation module homomorphism f:(M,d).rarw.(N, .delta.) is an A-homomorphism f:M.rarw.N such that f.d=.delta.. A derivation module of A, (U, d), there exists a unique derivation module homomorphism f:(U, d).rarw.(M,.delta.). In fact, a universal derivation module of A exists in the category of derivation modules of A, and is unique up to unique derivation module isomorphisms [2, pp. 101]. When (U,d) is a universal derivation module of R-algebra A, the A-module U is denoted by U(A/R). For out convenience, U(A/R) will also be called a universal derivation module of A, and d the R-derivation corresponding to U(A/R).

• KSCE Journal of Civil and Environmental Engineering Research
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• v.4 no.1
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• pp.93-101
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• 1984

New formulas to determine the critical elastic buckling load of long tapered columns are given. This study is restricted to solid round or rectangular columns with fixed-free ends as often used in highway design. The exact solution of the differential equation of the deflection curve is expressed in terms of Bessel Function and the solution is numerically evaluated using Bisection method by computer. In the F.E.M analysis of columns under their own weight, the stability problem can be resulted in a eigen value problem of conservative system. Approximate solution by the F.E.M is evaluted numerically using Jacobi method and compared with exact solution of the prismatic column to increase the precision. In addition, critical buckling load of the tapered column for every shape factor and ratio of cross-sectional change (Diameter of bottom end/Diameter of upper end) was converted into a comparable expression to critical buckling load of the prismatic column.

• The Pure and Applied Mathematics
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• v.11 no.1
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• pp.97-102
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• 2004

In this paper we establish some recurrence relations satisfied by quotient moments of upper record values from the Pareto distribution. Let ｛$X_n,n\qeq1$｝be a sequence of independent and identically distributed random variables with a common continuous distribution function(cdf) F($chi$) and probability density function(pdf) f($chi$). Let $Y_n\;=\;mas{X_1,X_2,...,X_n}$ for $ngeq1$. We say $X_{j}$ is an upper record value of {$X_{n},n\geq1$}, if $Y_{j}$＞$Y_{j-1}$,j＞1. The indices at which the upper record values occur are given by the record times ${u( n)}n,\geq1$, where u(n) = min{j｜j ＞u(n-l), $X_{j}$＞$X_{u(n-1)}$,n\qeq2$ and u(l) = 1. Suppose $X{\epsilon}PAR(\frac{1}{\beta},\frac{1}{\beta}$ then E$(\frac{{X^\tau}}_{u(m)}}{{X^{s+1}}_{u(n)})\;=\;\frac{1}{s}E$ E$(\frac{{X^\tau}}_{u(m)}{{X^s}_{u(n-1)}})$ - $\frac{(1+\betas)}{s}E(\frac{{X^\tau}_{u(m)}}{{X^s}_{u(n)}}$ and E$(\frac{{X^{\tau+1}}_{u(m)}}{{X^s}_{u(n)}})$ = $\frac{1}{(r+1)\beta}$ [E$(\frac{{X^{\tau+1}}}_u(m)}{{X^s}_{u(n-1)}})$ - E$(\frac{{X^{\tau+1}}_u(m)}}{{X^s}_{u(n-1)}})$ - (r+1)E$(\frac{{X^\tau}_{u(m)}}{{X^s}_{u(n)}})$]

• The Korean Journal of Physiology
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• v.17 no.1
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• pp.1-11
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• 1983

1) The two microelectrode method was used to voltage clamp small preparations of rabbit sinoatrial node. The kinetics of hyperpolarization activated inward current, $i_f$ were analysed. 2) The hrperpolarization pulses activated $i_f$ current in the presence of $10^{-7}g/ml$ TTX and 2 mM $Mn^{2+}$. The activation range was in between -45 mV to -75 mV. The current magnitude was increased and time course was faster by strong hyperpolarization pulses. 3) Standard envelope tests indicated that this current is exponentially controlled by single gate. 4) Semilogarithmic plot of $i_f$ activation versus time was found to be linear in the activation range. The decrease in current magnitude and the shifts in activation curve and rate constants curve to the hyperpolarizing direction were obtained with $Ba^{2+}$, indicating that $Ba^{2+}$ shifts the voltage dependence of the gating kinetics, were partially reversed by 24 mM $K^+$.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.2
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• pp.57-65
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• 1995

The effects of device geometry and layout on high speed performance such as current gain outoff frequency(f$_{T}$) and maximum oscillation frequency(f$_{max}$) are of very improtant for the scaling-down of geterojunction bipolar transistors(HBT$_{s}$). In this paper AlGaAs/GaAs HBTs are fabricated by MBE epitaxial growth and conventional mesa process, and the experimental data of emitter-base geometru dependency of HBT performance are presented in order to provide the quantitative information for optimum device structure design. It is shown that f$_{T}$ and f$_{max}$ are inversely proportional to the emiter stripe width, while the low emitter perimeter/area ratio is better to f$_{T}$ and worse ot f$_{max}$. It is also demonstrated the f$_{T}$ and f$_{max}$ are highly improved by the emitter-base spacing reduction resulting in less parsitic effects. As the result f$_{T}$ of 42GHz and f$_{max}$ of 23GHz are obtained for fabricated HBT with emitter area of 3${\times}20^{\mu}m^{2}$ and E-B spacing of 0.2$\mu$m.m.m.