• YAKHAK HOEJI
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• v.51 no.1
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• pp.56-62
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• 2007

Twelve epoxy and hydroxydiosgenin derivatives (DI-1${\sim}$DI-12) were synthesized from diosgenin (25(R)-5-spirosten-3${\beta}$-ol). Diosgenin was epoxidized with m-chloroperoxybenzoic acid (mCPBA) to oxidize 25(R)-4${\alpha}$,5${\alpha}$-epoxyspirostane (DI-1). Diosgenin was reacted with DDQ to form 25(R)-1,4,6-spirostatrien-3-one (DI-2), which was treated with 30% H$_2$O$_2$ to give 25(R)-1${\alpha}$,2${\alpha}$-epoxy-4,6-spirostadien-3-one (DI-3) and treated with mCPBA to form 25(R)-6${\alpha}$,7${\alpha}$-epoxy-1,4-spirostadien-3-one (DI-7), respectively. DI-3 was reduced with NaBH$_4$ to afford 25(R) -1${\alpha}$,2 ${\alpha}$-epoxy-4,6-spirostadien-3${\beta}$-ol(DI-4) and reacted with Li metal in absolute ethanol to form 25(R)-2-ethoxy-1,4,6-spirostatrien-3-one (DI-5). DI-7 was reduced with NaBH$_4$ to produce 25(R)-3${\beta}$,7${\alpha}$-dihydroxy-4-spirostene (DI-8) and treated with Li metal in liquid ammonia to produce 25(R)-7${\alpha}$-hydroxy-4-spirosten-3-one (DI-9). DI-2 was reduced with NaBH$_4$ to form 25(R) -4,6-spirestadien-3${\beta}$-ol(DI-10), which was stirred with 30% H$_2$O$_2$ to synthesize 25(R)-4,6-spirostadien-3-one (DI-11) and reacted with mCPBA to give 25(R)-4${\beta}$,5${\beta}$ -epoxy-6-spirosten-3${\beta}$-ol (DI-12), respectively. The antinociceptive effects of synthesiz ed compounds were measured by hot plate method and compound DI-7 signifcantly exhibited antinociceptive effect. DI-2 decreased the serum triglyceride and total cholesterol levels in poloxamer P-407 injected rat.

• Bulletin of the Korean Mathematical Society
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• v.56 no.4
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• pp.1027-1039
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• 2019

The concept of jump concerns the distribution of $Tur{\acute{a}}n$ densities. A number ${\alpha}\;{\in}\;[0,1)$ is a jump for r if there exists a constant c > 0 such that if the $Tur{\acute{a}}n$ density of a family $\mathfrak{F}$ of r-uniform graphs is greater than ${\alpha}$, then the $Tur{\acute{a}}n$ density of $\mathfrak{F}$ is at least ${\alpha}+c$. To determine whether a number is a jump or non-jump has been a challenging problem in extremal hypergraph theory. In this paper, we give a way to generate non-jumps for hypergraphs. We show that if ${\alpha}$, ${\beta}$ are non-jumps for $r_1$, $r_2{\geq}2$ respectively, then $\frac{{\alpha}{\beta}(r_1+r_2)!r_1^{r_1}r_2^{r_2}}{r_1!r_2!(r_1+R_2)^{r_1+r_2}}$ is a non-jump for $r_1+r_2$. We also apply the Lagrangian method to determine the $Tur{\acute{a}}n$ density of the extension of the (r - 3)-fold enlargement of a 3-uniform matching.

• Wind and Structures
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• v.29 no.1
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• pp.43-53
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• 2019

Vortex-induced vibration of three circular cylinders (each of diameter D) in an equilateral triangular arrangement is investigated using the immersed boundary method. The cylinders, with one placed upstream and the other two side-by-side downstream, are free to vibrate in the cross-flow direction. The cylinder center-to-center spacing L is adopted as L/D = 2.0. Other parameters include the Reynolds number Re = 100, mass ratio $m^*=2.0$, reduced velocity $U_r=2{\sim}15$ and damping ratio ${\zeta}=0$. Cylinder vibration responses are dependent on $U_r$ and classified into five regimes, i.e. Regime I ($U_r{\leq}3.2$), Regime II ($3.2<U_r{\leq}5.0$), Regime III ($5.0<U_r{\leq}6.4$), Regime IV ($6.4<U_r{\leq}9.2$) and Regime V ($U_r>9.2$). Different facets of vibration amplitude, hydrodynamic forces, wake patterns and displacement spectra are extracted and presented in detail for each regime.

• Geomechanics and Engineering
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• v.29 no.5
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• pp.523-533
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• 2022

Several prediction model of penetration rate (PR) of tunnel boring machines (TBMs) have been focused on applying to design stage. In construction stage, however, the expected PR and its trends are changed during tunneling owing to TBM excavation skills and the gap between the investigated and actual geological conditions. Monitoring the PR during tunneling is crucial to rescheduling the excavation plan in real-time. This study proposes a sequential prediction method applicable in the construction stage. Geological and TBM operating data are collected from Gunpo cable tunnel in Korea, and preprocessed through normalization and augmentation. The results show that the sequential prediction for 1 ring unit prediction distance (UPD) is R²≥0.79; whereas, a one-step prediction is R²≤0.30. In modeling algorithm, a gradient boosted regression tree (GBRT) outperformed a least square-based linear regression in sequential prediction method. For practical use, a simple equation between the R² and UPD is proposed. When UPD increases R² decreases exponentially; In particular, UPD at R²=0.60 is calculated as 28 rings using the equation. Such a time interval will provide enough time for decision-making. Evidently, the UPD can be adjusted depending on other project and the R² value targeted by an operator. Therefore, a calculation process for the equation between the R² and UPD is addressed.

• Journal of the Korean Applied Science and Technology
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• v.26 no.2
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• pp.205-212
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• 2009

Solution copolymerization of Styrene(St.) with 2-Hydroxypropylacrylate(2-HPA) was carried out with Benzoylperoxide(BPO) as an initiator in toluene at $80^{\circ}C$ in a batch reactor. Reaction volume and reaction time were 0.3 liters, 8 hours respectively. The time to reach steady state was about the six time. The monomer reactivity ratios, $r_1$(St.) and $r_2$(2-HPA) were determined by both the Kelen-Tudos method and the Fineman-Ross method ; $r_1$(St.)=0.376(0.330), $r_2$(2-HPA)=0.408(0.778). The activation energy of thermal decomposition was in the range of $33{\sim}55kcal/mol$.

• Bulletin of the Korean Mathematical Society
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• v.49 no.2
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• pp.295-306
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• 2012

Let (R, $m_R$, k) be a local maximal commutative subalgebra of $M_n$(k) with nilpotent maximal ideal $m_R$. In this paper, we will construct a maximal commutative subalgebra $R^{ST}$ which is isomorphic to R and study some interesting properties related to $R^{ST}$. Moreover, we will introduce a method to construct an algebra in $MC_n$(k) with i($m_R$) = n and dim(R) = n.

• Journal of Ocean Engineering and Technology
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• v.7 no.2
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• pp.91-102
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• 1993

The elastic-plastic fracture thoughness J sub(IC) of Nuclear Reactor Vessel Steel(SA 508-3) which has high toughness was discussed at temperatures RT, $-20^{\circ}C$, $200^{\circ}C$ and 1/2/CT specimen was used for this study. Especially the two methods recommended in ASTM and JSME were compared. It was difficult to find J sub(IC) by ASTM R-curve method with the specimen used for this research, while JSME R-curve method yielded good result. The stretched zone width menthod gave slightly larger J sub(IC) values than those by the R-curve method for SA 508-3 steel.

• Communications of the Korean Mathematical Society
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• v.12 no.2
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• pp.393-401
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• 1997

Let $A_1,A_2,\cdots,A_m$ and $B_1,B_2,\cdots,B_n$ be two sequences of events on a given probability space. Let $X_m$ and $Y_n$, respectively, be the number of those $A_i$ and $B_j$, which occur we establish new upper and lower bounds on the probability $P(X=r, Y=t)$ which improve upper bounds and classical lower bounds in terms of the bivariate binomial moment $S_{r,t},S_{r+1,t},S_{r,t+1}$ and $S_{r+1,t+1}$.

• Journal of the Chungcheong Mathematical Society
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• v.24 no.3
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• pp.553-560
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• 2011

We introduce a method to construct some algebras $R{\in}MC_n(k)$ with dim(R) = n and $dim(m_R^2)=1$ for each $n{\geq}3$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.337-340
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• 1999

Since the first reports of CMR(colossal magnetoresistance) effects in some single crystal R-P Phase Ln$_{1-x}$ Sr$_{2-x}$Mn$_{2}$O$_{7}$ 1996. many researches have been carried out to find optimum compositions and processing conditions in this system. In this study, layered perovskite R-P Phase Ln$_{1-x}$ Sr$_{2-x}$Mn$_{2}$O$_{7}$ (x=0.4, Ln=-La, Eu, Gd, Nd, Pr, Sm) phases were synthesized by solid state reaction and their structures were refined by Rietveld method. Electrical and magnetic properties were measured drown to 20K and compare with those of R-P Phase Ln$_{1-x}$ Sr$_{2-x}$Mn$_{2}$O$_{7}$ Phases.es.es.es.es.es.