• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2021.11a
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• pp.124-126
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• 2021

해양에서의 선박 대 선박, 선박 대 시설 등 장비 간 통신 서비스를 제공하기 위한 M-S2X 기술 적용 시 발생할 수 있는 보안 위협을 분석하고, 적용 가능한 보안요구사항을 도출하였다.

• Journal of applied mathematics & informatics
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• v.22 no.1_2
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• pp.361-372
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• 2006

In this paper, we consider the multi-point boundary value problems for one-dimensional p-Laplacian at resonance: $({\phi}_p(x'(t)))'=f(t,x(t),x'(t))$, subject to the boundary value conditions: ${\phi}_p(x'(0))={\sum}^{n-2}_{i=1}{\alpha}_i{\phi}_p(x'({\epsilon}i)),\;{\phi}_p(x'(1))={\sum}^{m-2}_{i=1}{\beta}_j{\phi}_p(x'({\eta}_j))$ where ${\phi}_p(s)=/s/^{p-2}s,p>1,\;{\alpha}_i(1,{\le}i{\le}n-2){\in}R,{\beta}_j(1{\le}j{\le}m-2){\in}R,0<{\epsilon}_1<{\epsilon}_2<...<{\epsilon}_{n-2}1,\;0<{\eta}1<{\eta}2<...<{\eta}_{m-2}<1$, By applying the extension of Mawhin's continuation theorem, we prove the existence of at least one solution. Our result is new.

• Honam Mathematical Journal
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• v.27 no.3
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• pp.399-404
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• 2005

Let M be a finite commutative nilpotent algebra over a perfect field k of prime characteristic p and let $M^p$ be the sub-algebra of M generated by $x^p$, $x{\in}M$. Eggert[3] conjectures that $dim_kM{\geq}pdim_kM^p$. In this paper, we show that the conjecture holds for $M=R^+/I$, where $R=k[X_1,\;X_2,\;{\cdots},\;X_t]$ is a polynomial ring with indeterminates $X_1,\;X_2,\;{\cdots},\;X_t$ over k and $R^+$ is the maximal ideal of R generated by $X_1,\;X_2,{\cdots},\;X_t$ and I is a monomial ideal of R containing $X_1^{n_1+1},\;X_2^{n_2+1},\;{\cdots},\;X_t^{n_t+1}$ ($n_i{\geq}0$ for all i).

• Bulletin of the Korean Mathematical Society
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• v.55 no.4
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• pp.1103-1107
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• 2018

Let M be a complete spacelike hypersurface in the (n + 1)-dimensional Minkowski space ${\mathbb{L}}^{n+1}$. Suppose that every unit speed curve X(s) on M satisfies ${\langle}X^{\prime\prime}(s),X^{\prime\prime}s){\rangle}{\geq}-1/r^2$ and there exists a point $p{\in}M$ such that for every unit speed geodesic X(s) of M through the point p, ${\langle}X^{\prime\prime}(s),X^{\prime\prime}s){\rangle}=-1/r^2$ holds. Then, we show that up to isometries of ${\mathbb{L}}^{n+1}$, M is the hyperbolic space $H^n(r)$.

• Bulletin of the Korean Mathematical Society
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• v.39 no.2
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• pp.277-282
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• 2002

We Show that When ($M,\;\omega$) is a closed, simply connected, symplectic manifold for all $\gamma\;\in\;\pi_1(Ham(M),\;id)$ the following inequality holds: $\parallel\gamma\parallel\;{\geq}\;sup_{\={x}}\;|A(\={x})|,\;where\;\parallel\gamma\parallel$ is the coarse Hofer's norm, $\={x}$ run over all extensions to $D^2$ of an orbit $x(t)\;=\;{\varphi}_t(z)$ of a fixed point $z\;\in\;M,\;A(\={x})$ the symplectic action of $\={x}$, and the Hamiltonian diffeomorphisms {${\varphi}_t$} of M represent $\gamma$.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.18 no.2
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• pp.3-10
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• 2008

The choice of basis for representation of element in $GF(2^m)$ affects the efficiency of a multiplier. Among them, a multiplier using redundant representation efficiently supports trade-off between the area complexity and the time complexity since it can quickly carry out modular reduction. So time of a previous multiplier using redundant representation is faster than time of multiplier using others basis. But, the weakness of one has a upper space complexity compared to multiplier using others basis. In this paper, we propose a new efficient multiplier with consideration that polynomial exponentiation operations are frequently used in cryptographic hardwares. The proposed multiplier is suitable fer left-to-right exponentiation environment and provides efficiency between time and area complexity. And so, it has both time delay of $T_A+({\lceil}{\log}_2m{\rceil})T_x$ and area complexity of (2m-1)(m+s). As a result, the proposed multiplier reduces $2(ms+s^2)$ compared to the previous multiplier using equally-spaced polynomials in area complexity. In addition, it reduces $T_A+({\lceil}{\log}_2m+s{\rceil})T_x$ to $T_A+({\lceil}{\log}_2m{\rceil})T_x$ in the time complexity.($T_A$:Time delay of one AND gate, $T_x$:Time delay of one XOR gate, m:Degree of equally spaced irreducible polynomial, s:spacing factor)

• Proceedings of the Korean Magnestics Society Conference
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• 2000.09a
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• pp.251-265
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• 2000

S $m_{2}$F $e_{17}$ $N_{x}$ film magnets using a S $m_{2}$F $e_{17}$ target were prepared at $N_{2}$ gas atmosphere using a Nd-YAG laser ablation technique. The effect of nitrogen pressure, deposition temperature, pulsation time and film thickness on the structure and magnetic properties of S $m_{2}$F $e_{17}$ $N_{x}$ film were studied. Increasing the nitrogen pressure up to 5 atm. was confirmed to lead the formation of complete S $m_{2}$F $e_{17}$ $N_{x}$ compound. Optimized magnetic properties with the nitrogenation temperature ranging over 500-53$0^{\circ}C$ could be obtained by extending the nitrogenation time up to 4 hours. Relatively low coercivities of 400~600 Oe were exhibited from the S $m_{2}$F $e_{17}$ $N_{x}$ films having the thickness of 50~100 nm while 4$\pi$ $M_{s}$ of 10~12 kG could be achieved. In-plane anisotropic characteristic, which was the basic goal in this study, was achieved by controlling the nitrogenation parameters.ameters.ers.ameters.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.32 no.4
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• pp.372-380
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• 1996

The operation of Far East Chain(GRI 5970) of Loran - C system had been stopped on June, 1995, but that of Korean Chain(GRI 9930) of Loran - C system which was jointed with North West Pacific Chain(GRI 8930) and Russia Chain(GRI 7950) by international cooperation, was started on January 1996. In this paper, in order to study the accuracy of Loran - C fix of Korean Chain, the authors examined and analyzed the data of the reciever of Loran - C(LC -90, Furuno) and GPS(AccNav Sport super (TM), Eagle) measured automatically and continually for 2 seconds at interval of 5 minutes from November 22, 1992, to January 20, 1996 at the fixed position of National Fisheries University of Pusan, The results obtained were as follows ; 1)The mean time differences of M-W, M-X, and M-Y pair measured in the base observed position were 12333.09${\mu}$s, 28338.44${\mu}$s, and 42806.01${\mu}$s respectively and the mean standard deviations of that were 0.0121${\mu}$s, 0.0290${\mu}$s, and 0.0327${\mu}$s respectively. The daily and monthly variance forms of time difference at each pair appeared in a similar reappearance. 2)The mean standard deviations of the latitude and longitude by Loran - C were 9.1m and 17.4m in W.X pair, 11.5m and 13.7m in W.Y pair, and 8.1m and 29.3m in X.Y pair respectively, and then the probable radiuses within 95% of each pair were 39.2m, 35.7m, and 60.8m, respectively. Therefore, It is to be desired that W.Y par is selected to improve the accuracy in Pusan area. 3)The mean standard deviations of the latitude and longitude by GPS were 15.4m and 15.0m and the probable radius within 95% was 43.4m. 4)The position errors for GPS and each pair of Loran - C were 16.0m to the South in GPS and 265.2m to the East in W.X pair of Loran - C, 279.5m to the North in W.Y pair of that, and 224.3m to the North-West in X.Y pair of that, so GPS is about 250m higher than Loran - C in accuracy.

• Communications of the Korean Mathematical Society
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• v.22 no.2
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• pp.183-194
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• 2007

For an irreducible binomial polynomial $f(x)=x^n-b{\in}K[x]$ with a field K, we ask when does the mth iteration $f_m$ is irreducible but $m+1th\;f_{m+1}$ is reducible over K. Let S(n, m) be the set of b's such that $f_m$ is irreducible but $f_{m+1}$ is reducible over K. We investigate the set S(n, m) by taking K as the rational number field.

• Journal of Integrative Natural Science
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• v.7 no.4
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• pp.283-285
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• 2014

We investigate irreducibility of the quadrinomial $F_m(x)=x^{2m}-x^{m+1}-x^{m-1}-1$ where m is an even integer ${\geq}2$ using only basic techniques that can be often used in many classes of polynomials.