• Journal of Integrative Natural Science
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• v.9 no.2
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• pp.94-102
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• 2016

The crystal structure of the potential active 6-ethoxy-3-phenyl-5a,9a-dihydro-3H-chromen[4,3-c][1,2]oxazole-3a(4H)-carbonitrile ($C_{19}H_{15}N_2O_3$) has been determined from single crystal X-ray diffraction technique. The title compound crystallizes in the monoclinic space group C2/c with unit cell dimension a= 29.3026(9) ${\AA}$, b= 6.7695(2) ${\AA}$ and c= 19.7597(6) ${\AA}$ [${\alpha}= 90^{\circ}$, ${\beta}= 125.709(10)^{\circ}$ and ${\gamma}= 90^{\circ}$]. Single crystals suitable for X-ray diffraction were obtained by slow evaporation method, the isoxazole and six membered pyran rings adopts envelope conformation. The crystal packing of the molecules is stabilized by the weak $C-H{\ldots}N$ hydrogen bond interaction.

• The Journal of Advanced Prosthodontics
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• v.6 no.6
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• pp.451-455
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• 2014

PURPOSE. The most common failure seen in restorations with a zirconia core is total or layered delamination of the ceramic veneer. In the present study, the shear bond strengths between veneering ceramics and colored zirconia oxide core materials were evaluated. MATERIALS AND METHODS. Zirconia discs ($15{\times}12{\times}1.6mm$) were divided into 11 groups of 12 discs each. Groups were colored according to the Vita Classic scale: A3, B1, C4, D2, and D4. Each group was treated with the recommended shading time for 3 s, or with prolonged shading for 60 s, except for the control group. Samples were veneered with 3 mm thick and 3.5 mm in diameter translucent ceramic and subjected to shear test in a universal testing machine with a crosshead speed of 1 mm/min. One-way analysis of variance (ANOVA) and Tukey's HSD tests were used for comparisons of the groups having the same shading times. A paired t-test was used for groups of the same color (3 s/60 s). RESULTS. Among the 11 groups investigated C4 (3 s) had the highest bond strength with a value of 36.40 MPa, while A3 (3 s) showed the lowest bond strength with a value of 29.47 MPa. CONCLUSION. Coloring procedures can affect zirconia/ceramic bond strength. However, the results also showed that bond strengths of all the investigated groups were clinically acceptable.

• Journal of the korean academy of Pediatric Dentistry
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• v.8 no.1
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• pp.77-88
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• 1981

The purpose of this study was to make a comprehensive study & evaluation of the oral status of mental retarded children. The auther examined intraorally 486 (male; 311, female;175) mental retarded children. The result was as follows; (General mental retarded children means the children who live in their parent's home, & orphan mental retarded children means the children who live in orphanage.) 1. The dft rate was 31.6% in general mental retarded children (G.m.r.c.) & 20.7% in orphan mental retarded children (O. m. r. c.). The dft index was 3.73 in G.m.r.c. & 2.15 in O.m.r.c. 2. The DMFT rate was 24.6% in female G.m.r.c., 16.7% in male G.m.r.c., 12.7% in female O.m.r.c., 8.4% in male O.m.r.c. The DMFT index was 4.94 in female G.m.r.c., 4.01 in male G.m.r.c., 1.40 in male O.m.r.c., 2.75 in female O.m.r.c. 3. The malocclusion prevalence was 57.3%. the class I malocclusion was 14.2% Class II malocclusion 19.3%, Class III malocclusion 23.5%. The children with Down's syndrome had 60.0% of class III malocclusion prevalence. 4. The dental calculus index was 1.97 in male O.m.r.c., 1.81 in female O.m.r.c., 1.30 in male G.m.r.e., 1.13 in female G.m.r.c. 5. The dental plaque index was 3.06 in female G.m.r.c., 3.00 in male Gm.r.e. 2.70 in male O.m.r,c., 2.32 in female O.m.r.c.

• Journal of the Korean Ceramic Society
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• v.40 no.3
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• pp.234-240
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• 2003

Hardened cement pastes of OPC which contains 10 wt% CSA type expansive additives were immersed in aqueous solution of 10 wt% MgS $O_4$.7$H_2O$ and then investigated by compressive strength, XRD. SEM and DSC etc.. According to the results including the hydration products and the microstructure of the hardened paste, the case of CSA type expansive additives［No. 6(C/(equation omitted) : 2.29, A/(equation omitted) : 0.16)] prepared from raw materials increased the resistance to $Mg^{2＋}$, S $O_4$$^{2-}$ ion diffusion than that of OPC paste due to the densification by the formation of fine ettringite in the first stage and the hydrates according to $\beta$-C$_2$S hydration in the late period.

• Journal of the Korean Ceramic Society
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• v.39 no.6
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• pp.610-615
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• 2002

Phase formation and proton conduction of L $a_{0.6}$B $a_{0.4}$I $n_{1-y}$ $M_{y}$ $O_{3-{\delta}}$(M=G $a^{3+}$, S $c^{3+}$, Y $b^{3+}$) system were studied. A cubic perovskite structure with a single phase was formed in all of the compositions of this work except for the composition off=G $a^{3+}$ with y=0.5, viz,L $a_{0.6}$B $a_{0.4}$I $n_{1-y}$G $a_{0.5}$ $O_{3-{\delta}}$ For the compositions of M=S $c^{3+}$and Y $b^{3+}$with y=0.25, proton conduction occurred in wet $N_2$ atmosphere(P $h_{H_2O}$=6.1hPa).X>/=6.1hPa).Pa).

• Journal of Species Research
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• v.11 no.3
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• pp.162-168
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• 2022

Compared to marine dinoflagellates, freshwater species are rarely recorded in Korea. In the present study, we isolated a freshwater dinoflagellate, Palatinus, from the Paldang Reservoir, Korea, in December 2021. The overall cell shape was ovoid, and the cell size was 34.3 ㎛ in length (25.8-39.5 ㎛) and 28.4 ㎛ in width (21.5-34 ㎛). An eyespot was usually observed near the sulcal region. The Kofoidian plate formula of the species was determined to be 4', 2a, 7", 6c, 5s, 5''', and 2''''. Apical pore complex was not observed. However, variations in the cingular plate caused by the fusion of 3C and 4C were observed. Analyses of 28S rDNA sequences revealed that the unidentified species is 100% similar to Palatinus apiculatus, and clustered together in the same lineage in the phylogenetic tree (100% bootstrap value). Our findings confirmed that the isolated dinoflagellate is Palatinus apiculatus, which was discovered for the first time in Korean freshwaters.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.4 no.3
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• pp.147-154
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• 1992

Laminar natural convection heat transfer from a hot body in a square enclosure has been studied for various center positions of a hot square at Grashof number $Gr=1.5{\times}10^5$, Prandtl number Pr=0.71 and dimensionless thermal conductivity $k_g/k_f=14710$. The natural convection at the center position of a hot square; $X_c$, $Y_c=0.5$, 0.2 shows the most strong and at $X_c$, $Y_c=0.5$, 0.7 the most weak. The total mean Nusselt number at $X_c$, $Y_c=0.5$, 0.2 was 7.4% higher than that at $X_c$, $Y_c=0.2$, 0.5. The total mean Nusselt number at $X_c$, $Y_c=0.5$, 0.7 was 5.0% lower than that at $X_c$, $Y_c=0.3$, 0.5.

• The korean journal of orthodontics
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• v.27 no.4 s.63
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• pp.539-548
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• 1997

The purpose of this study was to evaluate the effectiveness of gargling solution with 0.05% NaF and 10% Xylitol in orthodontic patients with fixed appliance. The sample consisted of 20 patients who were classified into an experimental group and a control group, 10 patients each. Experimental group was used experimental gargling solution and the control group was used with placebo solution. The change of S. mutans was analysed by culture on MSB and BHI agar plate pre and post 3, 6, 9 weeks. The results were as follows. 1 There were significant reduction in the number of S. mutans C.F.U. between pre and post 3 weeks(p<0.01), 9 weeks(p<0.05) in experimental group 2. There were significant reduction in the ratio of S. mutans C.F.U. to total C.F.U. between pre and post 3, 6, 9 weeks(p<0.01) in experimental group. 3. S. mutans, which were reduced until 3 weeks, did not show significant change after 3, 6, 9 weeks. 4. S. mutans were strongly suppressed until 3 weeks after gargling solution with 0.05% NaF and 10% Xylitol.

• Bulletin of the Korean Chemical Society
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• v.15 no.8
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• pp.658-662
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• 1994

Ab initio and extended Huckel calculations have been applied to discuss the electronic structure, ring inversion barrier, and geometry of the $Cp_2TiS_3$ compound. The deformation of four membered ring in the planar geometry is originated from a second-order Jahn-Teller distortion due to the small energy gap between HOMO and LUMO on the basis of extended Huckel calculations. The puckered $C_s$ geometry is stabilized by the interaction of the $x^2-y^2$ metal orbital with the hybrid orbital in sulfur. Ab initio calculations have been carried out to explore the ring inversion process for the model $Cl_2TiS_3$ compound. We have optimized $C_s$ and $C_{2v}$ structures of the model compound at the RHF level. The energy barriers for the ring inversion are sensitive to the used basis set. With 4-31$G^*$ for the Cl and S ligands, the barriers are computed to be 8.41 kcal/mol at MP2 and 8.02 kcal/mol at MP4 level.

• Journal of the Korean Society for Heat Treatment
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• v.3 no.4
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• pp.23-40
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• 1990

This study has been carried out to investigate into some effects of Mn content with varying amounts and austenite grain size on hardenability in boron-added Fe-C-Cr-Mo alloy systems. (1) Austenite grains have been found to hardly grow in the temperature range of $900^{\circ}C$ to $950^{\circ}C$, whereas they grow rapidly in the temperature range of $975^{\circ}C$ to $1100^{\circ}C$. (2) Austenite grain growth is considerably small with increasing holding time at a given austenitizing temperature and is, in particular, hardly found to occur at a temperature of $900^{\circ}C$. (3) The hardenability improves ramarkably as Mn content is increased at three different austenitizing temperatures $900^{\circ}C$, $1000^{\circ}C$ and $1100^{\circ}C$. (4) The maximum hardenability is obtained from steels A, B and C austenitized at the $900^{\circ}C$, although Mn content is varied in each specimen.