• Journal of Plant Biology
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• v.29 no.1
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• pp.53-65
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• 1986

The montane forests of Ulreung Island, Korea, were investigated by the ZM school method. By comparing the montane forests of this island with those of Korean Peninsula and of Japan, a new order, F a g e t a l i a m u l t i n e r v i s, a new alliance, F a l g i o n m u l t i n e r v i s, a new association, H e p a t i c o-F a g e t u m m u l t i n e r v i s and Rhododendron brachycarpum-Pinus parviflora community were recognized. The H e p a t i c o - F a g e t u m m u l t i n e r v i s was further subdivided into four subassociations; Subass. of Sasa kurilensis, Subass. of Rumohra standishii, Subass. of Rhododendron brachycarpum and Subass. of typicum. Each community was described in terms of floristic, structural and environmental features.

• Communications of the Korean Mathematical Society
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• v.39 no.1
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• pp.31-43
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• 2024

Let $R_e\,=\,\frac{{\mathbb{F}}_{p^m}[u]}{{\langle}u^e{\rangle}}$, where p is a prime number, e is a positive integer and u^e = 0. In this paper, we first characterize the structure of cyclic codes of length p^s over R_e. These codes will be classified into 2^e distinct types. Among other results, in the case that e = 4, the torsion codes of cyclic codes of length p^s over R₄ are obtained. Also, we present some examples of cyclic codes of length p^s over R_e.

• Bulletin of the Korean Mathematical Society
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• v.60 no.5
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• pp.1321-1334
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• 2023

An idempotent e of a ring R is called right (resp., left) semicentral if er = ere (resp., re = ere) for any r ∈ R, and an idempotent e of R∖{0, 1} will be called right (resp., left) quasicentral provided that for any r ∈ R, there exists an idempotent f = f(e, r) ∈ R∖{0, 1} such that er = erf (resp., re = fre). We show the whole shapes of idempotents and right (left) semicentral idempotents of upper triangular matrix rings and polynomial rings. We next prove that every nontrivial idempotent of the n by n full matrix ring over a principal ideal domain is right and left quasicentral and, applying this result, we can find many right (left) quasicentral idempotents but not right (left) semicentral.

• Journal of the Chungcheong Mathematical Society
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• v.9 no.1
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• pp.115-121
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• 1996

Let $\{X(t);\;t{\in}R^n\}$ be a measurable, separable and H-sssis random fields. Here, we suppose that the increments are invariant under all Euclidean rigid body motions. We investigate some properties of H-sssis random fields and monotonicity of projection process $\{X_e(t);\;t{\in}R^1\}$ in any direction $e{\in}R^n$.

• Journal of the Korean Mathematical Society
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• v.52 no.5
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• pp.991-1001
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• 2015

In this work we obtain conditions for nonspecial line bundles on general ${\kappa}$-gonal curves failing to be normally generated. Let L be a nonspecial very ample line bundle on a general ${\kappa}$-gonal curve X with ${\kappa}{\geq}4$ and $deg\mathcal{L}{\geq}{\frac{3}{2}}g+{\frac{g-2}{{\kappa}}}+1$. If L fails to be normally generated, then L is isomorphic to $\mathcal{K}_X-(ng^1_{\kappa}+B)+R$ for some $n{\geq}1$, B and R satisfying (1) $h^0(R)=h^0(B)=1$, (2) $n+3{\leq}degR{\leq}2n+2$, (3) $deg(R{\cap}F){\leq}1$ for any $F{\in}g^1_k $. Its converse also holds under some additional restrictions. As a corollary, a very ample line bundle $\mathcal{L}{\simeq}\mathcal{K}_X-g^0_d+{\xi}^0_e$ is normally generated if $g^0_d{\in}X^{(d)}$ and ${\xi}^0_e{\in}X^{(e)}$ satisfy $d{\leq}{\frac{g}{2}}-{\frac{g-2}{\kappa}}-3$, supp$(g^0_d{\cap}{\xi}^0_e)={\phi}$ and deg$(g^0_d{\cap}F){\leq}{\kappa}-2$ for any $F{\in}g^1_k$.

• The Journal of Korean Academy of Prosthodontics
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• v.39 no.5
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• pp.477-491
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• 2001

The purpose of this study is to compare and analyze the shade changes(${\Delta}E^*$) about $In-Ceram^{(R)}$, $IPS-Empress^{(R)}$, $OPC^{(R)}$ by using of the spectrophotometer arising from inital status and before and after cementation of the resin cement mounted on the metal core. We used a couple of statistics such as 'One- Way ANOVA' and 'Multiple Range Test.' We could be able to verify significantly what is being discussed here up to 95%. The results drawn from our research are as follows : 1. At the time of our experiments regarding the initial shapes of all-ceramic and mounting status of all-ceramic on the metal crown(${\Delta}E^*1$), and a comparison of mounting of all ceramic on the metal crown with all-ceramic cemented on the metal core(${\Delta}E^*2$), at the time of shade change of initial shapes and after we cemented on the metal core. (1) no significant difference among all-ceramics was found. (2) no particular difference was found regarding the $In-Ceram^{(R)}$. (3) a significant difference between the ${\Delta}E^*1$ and ${\Delta}E^*2$ regarding the $IPS-Empress^{(R)}$ was found(P<0.05). (4) a significant difference between the ${\Delta}E^*1$ and ${\Delta}E^*2$ regarding the $OPC^{(R)}$ was found(P<0.05). 2. When we compared the shade changes(${\Delta}E^*$) resulted from before and after the cementation on each of the parts involved of some all-ceramic, we could be able to find shade change increase form incisal third, middle third. and cervical third in that order in $In-Ceram^{(R)}$(spinell), IPS $Empress^{(R)}$, and $OPC^{(R)}$ all. In addition. we could be able to find a significant difference between cervical third and incisal third, middle third. (P<0.05) From what we have just seen, we might conclude that there is a significant shade change difference before and after the cementation with respect to $IPS-Empress^{(R)}$ and $OPC^{(R)}$. In addition, we could also be able to find more shade change difference at the cervical third rather than incisal third and middle third depending on the parts involved.

• Polymer Science and Technology
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• v.7 no.4
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• pp.364-370
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• 1996

• The Journal of the Petrological Society of Korea
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• v.16 no.1 s.47
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• pp.12-26
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• 2007

We have studied orientational characteristics of vertical rift and grain planes developing in 108 quarries for Mesozoic granites. Orientations of these planes vary in different localities. In general, orientations of these planes are predominantly NNE in South Korea. From the regional distribution chart, orientations of these planes show three dominant sets in terms of frequency orders: (1) $N2{\sim}10^{\circ}E(1st-order),\;(2)\;N15{\sim}25^{\circ}E(2nd-order),\;(3)\;N45{\sim}70^{\circ}E,\;N10{\sim}30^{\circ}W\;and\;N70{\sim}80^{\circ}W(3rd-order)$. These granite quarries are classified by the relative difference in the easiness of rock splitting between horizontal and vertical quarrying planes into: R-type, G-type, and H-type. The results showed that quarries for Triassic granites belong to R and G-types;those for Jurassic granites belong to R, G and H-types. In addition, quarries for Cretaceous granites belong mainly to R-type. Among these quarry types, the most diverse type was identified in the quarries for Jurassic granites. R-type (77.8%) shows a higher distribution ratio compared with G and H-types (22.2%). In general, anisotropy of physical properties is found in granitic rocks and there exists close correlation between orientations of granitic rock splitting planes and those of the open microcracks. Meanwhile, it has been reported that preferred orientations of open microcracks suggest maxinum principal stress orientations.

• Transactions on Electrical and Electronic Materials
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• v.1 no.1
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• pp.26-31
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• 2000

The ~1540 nm $^4$ $I_{13}$ 2/ longrightarro $w^4$ $I_{15}$ 2/ emissions of E $r^{3+}$ in Er-implanted GaN annealed at temperatures in the 400 to 100$0^{\circ}C$ range were investigated to gain a better understanding of the formation and dissociation processes of the various E $r^{3+}$ sites and the recovery of damage caused by the implantation with increasing annealing temperature ( $T_{A}$).The monotonic increase in the intensity of the broad defect photoluminescence(PL) bands with incresing $T_{A}$ proves that these are stable radiative recombination centers introduced by the implantation and annealing process. Theser centers cannot be attributed to implantation-induced damage that is removed by post-implantation annealing. Selective wavelength pumpling of PL spectra at 6K reveals the existence of at least nine different E $r^{3+}$ sites in this Er-implanted semiconductor. Most pf these E $r^{3+}$ PL centers are attributed to complexed of Er atoms with defects and impurities which are thermally activated at different $T_{A}$. Only one of the nine observed E $r^{3+}$ PL centers can be pumped by direct 4f absorption and this indicates that it is highest concentration E $r^{3+}$ center and it represents most of the optically active E $r^{3+}$ in the implanted sample. The fact that this E $r^{3+}$ center cannot be strongly pumped by above-gap light or broad band below-gap absorption indicates that it is an isolated center, i.e not complexed with defects or impurities, The 4f-pumped P: spectrum appears at annealing temperatures as low as 40$0^{\circ}C$, and although its intensity increase monotonically with increasing $T_{A}$ the wavelengths and linewidths of its characteristic peaks asre unaltered. The observation of this high quality E $r_{3+}$PL spectrum at low annealing temperatures illustrates that the crystalline structure of GaN is not rendered amorphous by the ion implantation. The increase of the PL intensities of the various E $R_{3+}$sites with increasing $T_{A}$is due to the removal of competing nonradiative channels with annealing. with annealing.annealing.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.27 no.1
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• pp.55-71
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• 1997

Digora/sup (R)/ an intraoral digital radiography system utilizing image plate (IP) - has a dynamic range of exposure time which allows it to decrease the patient's exposure time and to increase diagnostic ability through image processing, transmission and storage. The purpose of this study was to evaluate the Digora/sup (R)/ system by assessing the effects of various exposure times on the detectability on the tip of the endodontic file. Examining the root canals of 45 extracted sound premolars, K -files No. 10, 15, and 20 were placed at slightly varying distances from the apex. The teeth were glued onto resin-plaster blocks. Five exposure times varying between 0.01 seconds and 0.25 seconds were used. Four observers were asked to measure the distance between the tip of the file and a reduction of crown portion, and obtained mean errors (subtracting true file length from the measured file length), comparing Digora/sup (R)/ monitors with E-plus films, which were both obtained under the same geometrical positions. The results were as follows : 1. Comparing E-plus film with Digora/sup (R)/ at 0.01 seconds, the mean errors in E-plus film showed -4.453 nun, -4.497 nun, and -3.857 nun, while the mean errors in Digora/sup (R)/ showed 0.065 nun, 0.607 nun, and 0.719 mm according to the file groups. Therefore there was a significant difference between E-plus film and Digora/sup (R)/(p<0.05). 2. By comparison of mean errors according to the various exposure times in the Digora/sup (R)/ system, the mean error at 0.01 seconds was significantly lower than that at 0.12 and 0.25 seconds in the No. 10 file group(p<0.05). And the standard deviation was the highest at 0.01 seconds. 3. Comparing E-plus film at 0.25 seconds with the Digora/sup (R)/ system, the mean errors showed a significant difference between E-plus film at 0.25 seconds and the Digora/sup (R)/ system at 0.25 seconds in No. 10 and 20 file groups(p<0.05). 4. Comparing E -plus film at 0.25 seconds with other exposure times, the mean errors showed a significant difference between E-plus film at 0.25 seconds and E-plus film at 0 .. 01 and 0.03 seconds in 10 file group(p<0.05). In the No. 15 and 20 file groups, there was a significant difference between E-plus film at 0.25 seconds and E-plus film at 0.01 seconds(p<0.05). In conclusion, Digora/sup (R)/ was better than E-plus film in detectability on the tip of the file at the exposure time of 0.01 seconds in all file groups. And we concluded that Digora/sup (R)/ can shorten exposure times up to 4％ of 0.25 seconds (0.01 sec), which is adequate exposure time for premolar in E-plus film using No. 15 and 20 files.