• 치위생과학회지
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• 제22권3호
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• pp.156-163
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• 2022

Background: This study attempted to apply resin infiltrant (RI) as a method to maintain the effect of tooth bleaching treatment and compared it with fluoride varnish (FV) or artificial saliva to evaluate the effect. Methods: Sixty healthy lozenge specimens were classified into five groups. Group 1 was the negative control group, and discoloration was induced after artificial saliva treatment of the tooth specimen (G1_S+C). Group 2 was a positive control group, in which pigmentation was induced after bleaching treatment and artificial saliva treatment (G2 _B+S+C). Coloration was induced in group 3 (experimental group 1) after bleaching treatment and artificial saliva treatment, followed by application of fluorine varnish (G3_B+FV+S+C). Coloration was induced in Group 4 (experimental group 2) after applying RI after bleaching treatment and artificial saliva treatment (G4_B+RI+S+C). Pigmentation was induced in group 5 (experimental group 3) after bleaching treatment and artificial saliva treatment, followed by acid treatment (etching) and treatment with RI (G5_B+E+RI+S+C). Coffee and wine were used to induce discoloration. The lightness value (L^*) of the CIE L^*a^*b^* color system was obtained by image analysis. Kruskal-Wallis H analysis was performed for the mean difference in L^* values by group. Results: When coloration was induced with coffee, there was no significant difference in L^* value between artificial saliva (G2 _B+S+C), FV (G3_B+FV+S+C), and RI (G4_B+RI+S+C, G5_B+E+RI+S+C) groups. There was no significant difference in L^* values between the artificial saliva (G2 _B+S+C), FV (G3_B+FV+S+C), and RI (G4_B+RI+S+C, G5_B+E+RI+S+C) groups, even in the case of wine induced coloration. Conclusion: It was confirmed that artificial saliva or RI treatment had similar effects to the FV previously used to maintain the effect of tooth bleaching treatment.

• 한국농공학회지
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• 제34권1호
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• pp.78-86
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• 1992

This paper aims at investigating the effect of steel ratio and the magnitude of edge-ratio on the mechanical characteristics of reinforced concrete ring sector plate. The influence of steel bars was taken into account by coupling stiffness matrix of the steel bar element with that of the concrete plate element without dealing with separate element of steel bar and by establishing the composite stiffness matrix, which leads to the desirable result which does not increase th number of element could be obtained. Through case studies with 6 cases various steel ratios in ring sector plate supported at four edges and 4 cases with different open angles, the influence of the steel ratio was examined. A numerical analysis to find out the effect of the steel ratio d ue to above mentioned cases was carried out by 4 boundary conditions ; all edges clamped (B.C-1), all edges simply supported (B.C-2), curvilinear two edges clamped and other edges free (B.C-3) and curvilinear two edges simply supported and other edges free(B.C-4). The main results obtained are summarized as follows : 1. The effect of steel ratio on the magnitude of lateral deflection and x-directional bending moment at the center of sector plate and the midpoint of outer and inner curvilinear edges is almost the same up to $30^{\circ}$ of open angle. Beyond $30^{\circ}$ of the angle, the larger the angle, the greater the effect of ratio. 2. In design works using balanced steel ratio, the effect of steel bar can be ignored. But for larger open angles, especially greater than $90^{\circ}$, it proves desirable to consider the effect of steel bar. 3. The effect of the arc length of center circle/straight edge on lateral deflection and bending moment is remarkable in B.C-2. For larger open angle, the effect is also noted except for B.C-3 which turn out hardly affected. 4. The effect of the radius of curvature/straight side length on lateral deflection and x-directional bending moment is noted in B.C-2. As open angle increases, B.C-1 and B.C-3 almost agree and B.C-2 approaches B.C-4.

• 미생물학회지
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• 제40권2호
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• pp.154-159
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• 2004

돈분 고속발효에 적합한 미생물 제제를 개발하기 위하여 Bacillus속을 돈분에서 분리한 후,분리 균주의 생장능력, 효소활성 및 상호균주에 대한 항균활성을 비교 분석하였다. 분리된 4종을 동정한 결과, Bacillus cereus KD-2, B. pumilus KD-3, B. licheniformis KD-4로 분석되었고, 분리균주 KD-1은 그 어떤 Bacillus 종들과도 높은 일치성을 보이지 않았다. 생장최고온도는 Bacillus sp. KD-1이 $45^{\circ}C$, B. cereus KD-2가 $50^{\circ}C$, B. pumilus KD-3는 $53^{\circ}C$, B. licheniformis KD-4는 $55^{\circ}C$이었다. 이들 균주 모두를 혼합한 미생물 제제의 효소활성은 protease와 amylase는 37-$53^{\circ}C$ 범위에서 그 활성도에 차이를 보이지 않았고, lipase는 37-$42^{\circ}C$에서의 효소활성이 47-$53^{\circ}C$에 비해 2배 이상 높았다. 혼합 미생물 제제에 사용된 균주들의 상호 항균활성은 Bacillus sp. KD-1, B. cereus KD-2, B. pumilus KD-3는 타 균주의 생장에 영향을 주지 않았고, B. licheniformis KD-4의 배양 상층액을 10% (v/v)의 농도로 첨가시 다른 균주의 생장에 거의 영향을 주지 않았으나, 50% (v/v)로 혼합할 경우 다른 균주들의 생장을 억제하였다. 이 미생물 혼합 제제로 발효된 유기질비료의 성분은 유기물이 61.9%, 질소가 1.6%, C/N비가 22.4%, 인산이 0.21%, 칼리가 1.0%로 분석되었다. 발효 부산물인 액체비료의 암모니아 가스농도는 12.35 mg/1로 낮게 검출되었다.

• 폴리머
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• 제31권6호
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• pp.497-504
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• 2007

길이가 다른 폴리메틸렌 다리로 연결된 이핵 CGC(Constrained geometry catalyst) $[Zr({\eta}^5\;:\;{\eta}^1-C_9H_5-SiMe_2NCMe_3)Me_2]_2\;[(CH_2)_n]$ [n=6(4), 9(5), 12(6)]를 2 당량의 MeLi과 대응되는 염소화합물을 반응시켜 합성하고 이들의 구조를 확인하였다. 합성된 이핵메탈로센의 중합 특성을 에틸렌과 1-hexene의 공중합을 통해 조사하였다. 이때에 사용된 조촉매로는 일반 조촉매 $Ph_3C^+[B(C_6F_5)_4]^-\;(B_1)$과 $(B(C_6F_5)_5)_3\;(B_3)$ 그리고 이핵조촉매 $Ph_3C^+[(C_6F_5)_3B-C_6F_4-B(C_6F_5)_3]^{2-}\;(B_2)$을 이용하였다. 중합 결과 촉매의 활성은 이핵메탈로센에서는 다리길이가 길수록 크게 나타났으며, 조촉매에서는 이핵조촉매가 가장 낮은 활성을 보였다. 조촉매의 특성은 공중합체에 존재하는 가지의 함량에서 잘 나타났다. 이핵조촉매($B_2$)를 사용하면 가장 가지수가 작은 고분자가 생성되었고, 조촉매 $B_3$에서 가장 많은 가지를 가진 공중합체가 생성되었다.

• 한국분말재료학회지
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• 제16권2호
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• pp.110-114
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• 2009

Mechanical coating process was applied to form 89 %-hydrolyzed poly vinyl alcohol (PVA) onto boron carbide ($B_4C$) nanopowder using one step high energy ball mill method. The polymer layer coated on the surface of B4C was changed to glass-like phase. The average particle size of core/shell structured $B_4C$/PVA was about 50 nm. The core/shell structured $B_4C$/PVA was formed by dry milling. However, the hydrolyzed PVA of $98{\sim}99%$ with high glass transition temperature ($T_g$) was rarely coated on the powder. The $T_g$ of polymer materials was one of keys for guest polymer coating on to the host powder by solvent free milling.

• 한국분말재료학회지
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• 제20권5호
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• pp.366-370
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• 2013

The effects of $B_4C$ on the mechanical properties of WC/Ni-Si hardmetal were analyzed using sintered bodies comprising WC(70-x wt.%), Ni (28.5 wt.%), Si (1.5 wt.%), and $B_4C$ (x wt.%), where $$0{\leq_-}x{\leq_-}1.2$$ wt.%. Samples were prepared by a combination of mechanical milling and liquid-phase sintering. Phase and microstructure characterizations were conducted using X-ray diffractometry, scanning electron microscopy, and electron probe X-ray micro analysis. The mechanical properties of the sintered bodies were evaluated by measuring their hardness and transverse rupture strength. The addition of $B_4C$ improved the sinterability of the hardmetals. With increasing $B_4C$ content, their hardness increased, but their transverse rupture strength decreased. The changes of sinterability and mechanical properties were attributed to the alloying reaction between $B_4C$ and the binder metal (Ni, Si).

• Nuclear Engineering and Technology
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• 제46권5호
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• pp.675-680
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• 2014

Pulverization of two different sized micro-$B_4C$ particles (${\sim}10{\mu}m$ and ${\sim}150{\mu}m$) was investigated using a STS based high energy ball milling system. Shapes, generation of the impurities, and reduction of the particle size dependent on milling time and initial particle size were investigated using various analytic tools including SEM-EDX, XRD, and ICP-MS. Most of impurity was produced during the early stage of milling, and impurity content became independent on the milling time after the saturation. The degree of particle size reduction was also dependent on the initial $B_4C$ size. It was found that the STS nanoparticles produced from milling is strongly bounded with the $B_4C$ particles forming the $B_4C$/STS composite particles that can be used as a neutron absorbing nanocomposite. Based on the morphological evolution of the milled particles, a schematic pulverization model for the $B_4C$ particles was constructed.

• 한국토양동물학회지
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• 제5권2호
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• pp.85-96
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• 2000

Actinolaimoidea 상과에 속하는 4신종을 기재 하였다. Neoactinolaimus gosungensis n. sp.는 체장이 2.2-2.4 mm 이고, b = 4.3-4.9; c = 10.7-11.2; 교접자는 60-62 $mu extrm{m}$이다. 구순부는 낮고, 비대칭형인 창침과 넓은 관공을 가진다. Egtitus arcuatus n. sp.는 체장이 1.5-1.8 $\mu\textrm{m}$이고, b = 3.6-4.2; c = 14-15, 창침은 배부로 굽었고, 식도의 기부에 식도장간개가 있다. Paractinolaimus tuberculantus n. sp.는 체장이 1.9-2.5 mm이고, b = 3.3-4.0, c = 7.2-8.8, 교접자는 66-69 $\mu\textrm{m}$이고 특이하게 몸통이 꼬였고, 식도의 기부에 결절이 있다. Carcharolaimus koriensis n. sp.는 체장이 1.7-1.9 mm이고, b = 3.6-4.5, c = 65-76 그리고 표피에 매우 뜨겁고 창침공이 큰 것이 특징이다.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2002년도 춘계학술강연 및 발표대회
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• pp.65-66
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• 2002

• 한국결정성장학회지
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• 제18권2호
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• pp.62-67
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• 2008

유기금속 화합물 $C_{12}H_{20}B_{10}S_2Co_2$를 o-carborane으로 출발하여 $Cp^*Co(S_2B_2B_{10}H_{10})$을 합성하고, $BH_3{\cdot}THF$를 가하여 합성하였다. X-선 회절법을 이용하여 $C_{12}H_{20}B_{10}S_2Co_2$ 화합물의 분자구조를 규명하였다. 이 화합물의 결정학적 자료는 monoclinic, space group Cc, a=15.981(4) ${\AA}$, b=15.478(17) ${\AA}$, c=12.0562(17) ${\AA}$, ${\beta}=115.063(16)^{\circ}$, Z=4, V=9683(4) ${\AA}^3$이다. 결정 구조는 직접법으로 해석하였으며, 완전행렬최소자승법을 정밀화 하였으며 9948개의 회절 반점에 대하여 최종 신뢰도 인자 R=0.0630인 분자모형을 구하였다.