• Resources Recycling
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• v.23 no.1
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• pp.17-24
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• 2014

Solvent extraction experiments have been performed to separate Nd and Pr from chloride leaching solution of monazite sand using PC88A and D2EHPA. For this purpose, the effect of the saponification of PC88A and D2EHPA on the extraction and separation of the two metals were studied by varying the pH of aqueous solution. In the experimental ranges conducted in this study, the distribution coefficients of Nd were higher than those of Pr and separation factor value increased with the increase of solution pH. Saponification of PC88A enhanced the distribution coefficients of Nd and Pr as well as the separation factor. Saponification of D2EHPA had some effect on the extraction of the two metals but little effect on the separation factor.

• International Journal of Oral Biology
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• v.36 no.1
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• pp.31-35
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• 2011

Teeth develop via a reciprocal induction between the ectomesenchyme originating from the neural crest and the ectodermal epithelium. During complete formation of the tooth morphology and structure, many cells proliferate, differentiate, and can be replaced with other structures. Apoptosis is a type of genetically-controlled cell death and a biological process arising at the cellular level during development. To determine if apoptosis is an effective mechanism for eliminating cells during tooth development, this process was examined in the rat mandible including the developing molar teeth using the transferase-mediated dUTP-biotin nick labeling (TUNEL) method. The tooth germ of the mandibular first molar in the postnatal rat showed a variety of morphological appearances from the bell stage to the crown stage. Strong TUNEL-positive reactivity was observed in the ameloblasts and cells of the stellate reticulum. Odontoblasts near the prospective cusp area also showed a TUNEL positive reaction and several cells in the dental papilla, which are the forming pulp, were also stained intensively in this assay. Our results thus show that apoptosis may take place not only in epithelial-derived dental organs but also in the mesenchyme-derived dental papilla. Hence, apoptosis may be an essential biological process in tooth development.

• The Korean Journal of Food And Nutrition
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• v.28 no.5
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• pp.752-758
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• 2015

This study was conducted to investigate the antioxidant and anti-obesity activity of ethanol extracts from fermented Arctium lappa L. Arctium lappa fermented twice with Phellinus linteus ($2^{nd}$ FA) showed more DPPH radical scavenging activity than non-fermented Arctium lappa (NFA), and Arctium lappa fermented once ($1^{st}$ FA) at a concentration of 62.5 ppm. The $2^{nd}$ FA showed the highest level of ABTS radical scavenging activity at concentration range of 31.5~125 ppm. The ABTS free radical scavenging activities of $1^{st}$ FA and $2^{nd}$ FA were similar to that of BHA, a synthetic antioxidant, at a concentration of 250 ppm. The total polyphenol content of $2^{nd}$ FA was higher than those of NFA and $1^{st}$ FA. The flavonoid content was significantly increased in $1^{st}$ FA and $2^{nd}$ FA than NFA. During adipocyte differentiation, lipid accumulation in 3T3-L1 cells was significantly decreased in the order of NFA, $1^{st}$ FA, and $2^{nd}$ FA at all concentrations. In conclusion, the antioxidant and anti-obesity activities of A. lappa were increased depending on the degree of fermentation. It is suggested that fermented Arctium lappa, especially $2^{nd}$ FA, could be used as a natural ingredient for functional foods and medicine.

• Journal of the Korean Society of Safety
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• v.33 no.3
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• pp.39-45
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• 2018

The occupational safety and health act defines how to evaluate the explosion hazardous areas according to KS (Korean Industrial Standards). Current KS have to follow IEC (International Electrotechnical Commission) 60079-10-1 1st edition and there has been no change since 2008. And its 2nd edition has been revised in 2015. In this study, IEC 1st Ed. (IEC 60079-10-1 1st edition) is compared with IEC 2nd edition. Total 112 case studies including four materials (methane, propane, benzene, methanol) are selected to test and explosion hazardous ranges evaluated by IEC 1st and 2nd Ed. are analyzed according to various leakage pressures and hole sizes. In order to verify the results calculated by them, PHAST, which is one of the most representative consequence analysis programs, is employed. As a result, it can be concluded that there are many differences between IEC 1st and 2nd Ed. due to the discharge and the ventilation parameters. As comparing with PHAST, it is confirmed that IEC 1st provides more conservative values than PHAST. Even if IEC 2nd Ed. provides more conservative for gases, this fails to provide more conservative values for liquids. Therefore, it is worth to note that a large value between the explosion hazardous ranges value calculated by the IEC 1st Ed. and 2nd Ed. should be selected until further investigation and analysis is made. Morevover, the full consideration for IEC 2nd Ed. have to be needed.

• Journal of Magnetics
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• v.9 no.4
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• pp.101-104
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• 2004

The crystallization behaviours of nanocomposite made by a function of quenching rate (roller speed) were studied. The results showed that there was one step c$\mathbb{r}$ystallization process for the alloy quenched at roller speed of 32 m/s, which could be shown as, Am (amorphouse) + ${\alpha}-Fe/Nd_2Fe_{14}B$ ${\rightarrow}$ ${\alpha}-Fe/Nd_2Fe_{14}B$ . For the alloy quenched at roller speed of 40 m/s, there was steps crystallization process taking place at different temperatures, which could be shown as, Am ${\rightarrow}$ ${\alpha}-Fe/Nd_2Fe_{23}B_3+Nd_2Fe_{14}B+Am`$ ${\rightarrow}$ ${\alpha}-Fe/Nd_2Fe_{14}B$. The presence of transition phase ($Nd_2Fe_{23}B_3$) was harmful to get fine and uniform grain size during crystallization process. Uniform microstructures and high magnetic properties could be attained for the as-quenched alloy containing less amorphous phase and no presence of transition phase during annealing treatment. For the alloy prepared at roller speed of 32 m/s, the following properties were obtained, $B_r= 0.904 T,_iH_c = 801 kA/m, (BH)_{max} = 122 kJ/m^3 and M_r/M_s = 0.6$.

• Journal of Powder Materials
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• v.23 no.6
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• pp.432-436
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• 2016

We investigate the microstructural and magnetic property changes of $DyH_2$, $Cu+DyH_2$, and $Al+DyH_2$ diffusion-treated NdFeB sintered magnets with the post annealing (PA) temperature. The coercivity of all the diffusion-treated magnets increases with increasing heat treatment temperature except at $910^{\circ}C$, where it decreases slightly. Moreover, at $880^{\circ}C$, the coercivity increases by 3.8 kOe in Cu and 4.7 kOe in Al-mixed $DyH_2$-coated magnets, whereas this increase is relatively low (3.0 kOe) in the magnet coated with only $DyH_2$. Both Cu and Al have an almost similar effect on the coercivity improvement, particularly over the heat treatment temperature range of $790-880^{\circ}C$. The diffusivity and diffusion depth of Dy increases in those magnets that are treated with Cu or Al-mixed $DyH_2$, mainly because of the comparatively easy diffusion path provided by Cu and Al owing to their solubility in the Nd-rich grain boundary phase. The formation of a highly anisotropic $(Nd,\;Dy)_2Fe_{14}B$ phase layer, which acts as the shell in the core-shell-type structure so as to prevent the reverse domain movement, is the cause of enhanced coercivity of diffusion-treated Nd-Fe-B magnets.

• Journal of the Korean Ceramic Society
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• v.30 no.2
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• pp.101-106
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• 1993

Effects of CaO on microwave dielectric properties of (Ba, Pb)O-Nd2O3-TiO2 ceramic ystem were investigated. As the content of CaO increases, the sintered bulk density decreases due to the decrease of sinterability. However, with increasing the sintering tmperature, the relative dielectric constants increases. This has been attributed on the formation of the 2nd phase inclusion, TiO2(rutile). The Q values increase due to the compensation effect of Ca ions up to 1 wt%, and then decrease due to the interfacial relaxation effects. The temperature coefficient of resonance frequency increases to a positive direction with increasing the amounts of CaO.

• Journal of the Korean Society of Mechanical Technology
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• v.13 no.1
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• pp.95-103
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• 2011

Robots in various types carry and assemble parts through repeatedly and accurately moving to stored locations by combining linear motions. And, linear systems are used in orthogonal axes of robots and driven via ball screws, such as 2-axis cartesian coordinate robot in this paper. This paper presents the effect of the linear motion guide that is used in $2^{nd}$ axis in 2-axis cartesian coordinate robot. Some simulation results show that the linear motion guide influence greatly in robot performance such as the nominal life of linear guide. When use LM guide that have capacity near in $2^{nd}$ axis, this paper show that the nominal life on LM block of $1^{st}$ axis increases 37.4% and that the specification of $2^{nd}$ axis LM guide influences greatly the nominal life of $1^{st}$ axis LM block.

• The Journal of the Korean dental association
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• v.50 no.6
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• pp.329-338
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• 2012

Introduction: The purpose of this study is to evaluate the clinical results of vertical alveolar ridge augmentation using autogenous block bone graft, especially resorption rate, and outcomes of dental implants placed in the grafted site. Patients and Methods: Medical records and radiographs were reviewed. Twenty-seven patients who have been received the autogenous block bone graft which harvested from chin, ramus, and ilium, and the implant installation on 31 areas(22 maxillas and 9 mandibles) were included. Eight implants were installed simultaneously at the time of bone graft in 4 patients, and 65 implants were installed after 4.9 months(range 2~18 months) of autogenous block bone graft in 23 patients. The resorption amount and rate of augmented bone, and the success and survival rates implants were evaluated. Results: Mean height of the augmented block bone was $5.9{\pm}2.3mm$(range from 2.5 to 13.0 mm). Mean follow-up period after block bone graft was 30.4 months(range from 16 to 55 months). Mean resorption of the augmented block bone was $2.0{\pm}1.5mm$ (range from 0.5 to 7.24 mm). The success and survival rates of the implants were 78.1 % and 98.6%, respectively. Conclusion: This study indicates that the autogenous block bone graft is a useful and stable method for alveolar ridge augmentation for dental implant. And more augmentation is needed to compensate the resorption of the grafted bone.

• The Journal of the Petrological Society of Korea
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• v.1 no.2
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• pp.124-131
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• 1992

The Sm-Nd isotopic data on the Precambrian gneisses from Gyeonggi and Sobaegsan Massifs are presented and the crustal evolution of the Precambrian basements of the Korean Peninsula is discussed with that of the Precambrian basements of East Asia. Sm-Nd isochron plots on whole rock samples from Sobaegsan Massif give the following ages and initial Nd values. Biotite gneisses: $1.05{\pm}0.07$ Ga with ${\varepsilon}_{Nd}$ (1.05 Ga)= $-12.5{\pm}0.4$ ($2{\sigma}$); granitic gneisses: $1.70{\pm}0.59$ Ga with ${\varepsilon}_{Nd}$ (1.70 Ga)=$+9.5{\pm}6$($2{\sigma}$). Initial Nd isotopic evolution diagram for the Precambrian orthogneisses from Sobaegsan Massif with the Precambrian orthogneisses in northeastern China and Japan reveals the existence of early Archean depleted-mantle in east Asia and suggests the prevalence of nearly common or similar source accountable for these Precambrian gneisses. Such a common source is shown to have LREE-enriched feature and to have been formed from the depleted-mantle in the late Archean of ca. 2.6 Ga. On the other hand, the Sobaegsan granitic gneisses in Korea are concluded to have different evolution history. Our Sm-Nd study clearly discloses that some Precambrian orthogneisses from Korea had evolved from the protolith having the similar or same geochemical properties with the Precambrian orthogneisses in Japan and northeastern China. In addition, crustal formation age of Gyeonggi Massif in southern Korea may be different from that of Sobaegasn Massif.