• The Journal of Korean Society for School & Community Health Education
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• v.10 no.2
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• pp.55-68
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• 2009

연구목적: 본 연구는 미국 인디애나 주에 소재하는 중학교와 고등학교 학생들 사이의 methamphetamine, MDMA, GHB, and Rohypnol과 같은 약물사용 특성을 파악하고 청소년 약물사용과 관련된 성과 학교 환경에 대한 인지된 안전도 특성을 분석하였다. 연구방법: 본 분석에 사용된 데이터는 Indiana Prevention Resource Center (IPRC)에서 2007 년도에 수행한 음주, 흡연, 약물사용 설문조사(ATOD) 응답자료로서 인디애나 주에 거주하고 있는 6-12 학년 사이의 학생들을 편의추출하여 조사가 가능했던 158,632명의 응답을 얻었다. 연구결과: 로지스틱 회귀분석에서 조사한 4개 약물을 사용하는 학생들의 관심도는 교실에 있을 때, 복도에서 혼자 있을 때, 방과후 활동을 위해 학교에 남아있을 때 불안전하다고 느끼는 약물 미사용자보다 더 높은 경향을 보였다. GHB, MDMA, Rohypnol을 사용한다고 응답한 학생이 여자보다 남자에서 더 많았고 상관관계분석 결과, 메탐페타민을 비롯한 네 가지 약물 사용의 상호간 상관도가 모두 유의미하게 높았다.

• 한국정보교육학회:학술대회논문집
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• 2009.08a
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• pp.205-211
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• 2009

이 연구의 목적은 3D 가상공간인 세컨드라이프에서 예비교사의 성공적인 수업실습을 위한 수업실습장을 개발하는 것이다. 이를 위해 본 연구에서 수행한 내용은 다음과 같다. 첫째, 수업실습 관련 이론 탐색 및 문헌 연구를 통해 세컨드라이프에서의 수업실습의 가능성을 탐색하였다. 둘째, 가상공간의 특성에 대한 문헌 연구를 통해 가상공간에서 예비교사의 수업실습이 성공적인 경험이 되기 위한 조건들을 탐색하였다. 셋째, 이 조건들로부터 세컨드라이프에서의 수업실습 절차를 개발하였다. 넷째, 세컨드라이프에서 수업실습을 위해 필요한 실습장을 설계하고 개발하였다. 마지막으로, 세컨드라이프내의 교실 안에서 예비교사의 수업실습을 수행하였다. 이 수행결과에 기반하여 실습장의 구성요소를 수정.보완하여 개발을 완료하였다.

• Communications of Mathematical Education
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• v.22 no.2
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• pp.187-209
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• 2008

In this paper we analyze various russian studies related with differentiated mathematics education. Especially we work on the studies published in 1980-1995 years. As a result, we find that many studies are carried out with various view points in different directions, draw out essential variables, embodiment methods of differentiated mathematics education in Russia.

• Korean Journal of Dental Materials
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• v.45 no.4
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• pp.243-256
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• 2018

The purpose of this study was to investigate the effects of the anodization and cyclic calcification treatment on the surface characteristic and bioactivity of the titanium thin sheet in order to obtain basic data for the production of bioactive titanium membrane. A $30{\times}20{\times}0.08mm$ titanium sheets were prepared, and then they were pickled for 10 seconds in the solution which was mixed with $HNO_3:HF:H_2O$ in a ratio of 12: 7: 81. The $TiO_2$ nanotube layer was formed to increase the specific surface area of the titanium, and then the cyclic calcification treatment was performed to induce precipitation of hydroxiapatite by improvement of the bioactivity. The corrosion resistance test, wettability test and immersion test in simulated body solution were conducted to investigate the effect of these surface treatments. The nanotubes formed by the anodization treatment have a dense structure in which small diameter tubes are formed between relatively large diameter tubes, and their inside was hollow and the outer walls were coupled to each other. The hydroxyapatite precipitates were well combined on the nanotubes by the penetration into the nanotube layer by successive cyclic calcification treatment, and the precipitation of hydroxyapatite tended to increase proportionally after immersion in simulated body solution as the number of cycles increased. In conclusion, it was confirmed that induction of precipitation of hydroxyapatite by cyclic calcification treatment after forming the nanotube $TiO_2$ nanotube layer on the surface of the titanium membrane can contribute to improvement of bioactivity.

• Annals of Clinical Microbiology
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• v.18 no.2
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• pp.37-43
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• 2015

Background: Tuberculosis is globally the most important cause of death from single pathogen. Rapid and accurate identification of mycobacteria is essential for the control of tuberculosis. We evaluated a fluorescence in situ hybridization (FISH) method using peptide nucleic acid (PNA) probes for the differentiation of Mycobacterium tuberculosis complex (MTB) and nontuberculous mycobacteria (NTM) in direct smears of sputum specimens. Methods: The cross-reactivity of MTB- and NTM-specific PNA probes was examined with reference strains of M. tuberculosis ATCC 13950, Mycobacterium kansasii ATCC 12479, Mycobacterium fortuitum ATCC 6841, several clinical isolates of mycobacteria (Mycobacterium abscessus, Mycobacterium avium, Mycobacterium intracellulare, Mycobacterium gordonae and Mycobacterium chelonae), and 11 frequently isolated respiratory bacterial species other than mycobacteria. A series of 128 sputa (89 MTB culture positive, 29 NTM culture positive, and 10 under treatment culture negative) with grades of trace to 4+ were used to evaluate the performance of the method. Results: The MTB- and NTM-specific PNA probes showed specific reactions with the reference strains of MTB and M. kansasii and clinical isolates of mycobacteria except M. fortuitum ATCC 6841, and no cross-reactivity with other tested bacteria. The PNA probe-based FISH assay for detection of MTB had a sensitivity and specificity of 100%, respectively. The sensitivity and specificity of the NTM-specific PNA probe was 100%. The smear grades of the PNA FISH test were same as with those of the fluorescence AFB stain in 2+ or higher grade. Conclusion: Detection and differentiation based on PNA FISH is sensitive and accurate for detecting mycobacteria and for differentiating MTB from NTM in clinical sputum smears.

• Korean Journal of Dental Materials
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• v.44 no.2
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• pp.129-139
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• 2017

This study investigated the colors and mechanical properties of layered dental composites. Four nanocomposite resins (Aelite LS, Grandio, Tetric EvoCeram, Filtek Z350XT) and a silorane-based composite resin (P90) were used for overlying and underlying materials, respectively, with different thickness combinations. Colors, translucency parameter (TP), flexural and compressive properties were evaluated. All tested specimens had different color coordinates, although all were of A3 shade. Color coordinates and TP values of layered specimens better matched those of the corresponding overlying product as the thickness of the overlying product was increased. High TP values were related with high $b^*$ value differences between specimens (p<0.05). Both flexural strength and modulus, compressive strength and modulus of layered specimens with different thickness combinations were mostly lower than those of the corresponding overlying products, respectively, in their non-layered state.

• Korean Journal of Dental Materials
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• v.44 no.3
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• pp.263-272
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• 2017

In this study, antibacterial chlorhexidine (CHX)-containing hydroxyapatite (HAp) was coated on titanium and investigated its characteristics. Ti-mSBF-CHX group was prepared by soaking titanium disks in the modified simulated body fluid (mSBF) mixed with CHX. Ti-mSBF group was coated using mSBF without CHX. Ti-mSBF-adCHX group was prepared by soaking Ti-mSBF specimen in CHX-containing solution. The crystallines clusters composed with nano-shaped crystallites were coated on the surface of the Ti-mSBF specimen. The ribbon-shaped crystallites were observed with the crystalline clusters on the Ti-mSBF-CHX specimen. The content of CHX chemical compositions was high in ribbon-shaped crystallites. HAp crystalline structure was dominant for all prepared specimens, and ${\beta}-TCP$ (tricalcium phosphate) and OCP (octacalcium phosphate) crystalline structures were observed in the Ti-mSBF-CHX specimen. FT-IR spectra showed the strong peaks of CHX in Ti-mSBF-adCHX and Ti-mSBF-CHX groups. However, after immersing in a phosphate buffered saline (PBS), CHX was rapidly released in Ti-mSBF-adCHX group, while it was slowly released in Ti-mSBF-CHX. We expect that the coating method of Ti-mSBF-CHX group could be used for protecting inflammation of titanium implant by incorporating antibacterial agent CHX into HAp layer.

• Korean Journal of Dental Materials
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• v.44 no.2
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• pp.151-161
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• 2017

The purpose of this study was to examine the effect of shade and thickness of resin-nanoceramic CAD-CAM block (RNB) on the microhardness of dual-cured resin cement, as well as to measure the number of photons transmitted through RNBs of different thicknesses and colors. One dual-cured resin cement was used to prepare resin cement specimens. Resin cement specimens were light-cured for 40 seconds through 3 shades (A1, A2, A3 in HT (high translucency) and LT (low translucency) respectively) and four thicknesses (1, 2, 3, 4 mm) of RNB specimens. Vickers microhardness measurements of resin cement specimens were performed using a Vickers hardness tester. The light transmission of RNB specimens was measured using a spectrometer (SpectroPro-500, Acton Research, Acton, MA, U.S.A.), and the translucency parameter was calculated using the CIEL*a*b* system. Data were statistically analyzed by ANOVA and Tukey's test. There was a significant decrease of microhardness of resin cement specimen with an overlay of 4 mm of RNB thickness and A3 shade in comparison to A1 and 1 mm, respectively (p<0.05). The translucency parameter values and light transmission of RNBs tested differed significantly, according to the thicknesses of the specimen (p<0.05). Light transmission is decreased with increase in the thicknesses of RNBs. Shade A1 transmitted more light than darker blocks. A decrease in microhardness of resin cement specimens was observed with increasing thickness and shade (A1 to A3) of RNBs.

• Korean Journal of Dental Materials
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• v.44 no.4
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• pp.337-348
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• 2017

In this study, the effect of cooling rate control on the change in hardness of the multi-purpose Ag-Pd-Zn-In-Sn alloy during porcelain firing simulation and post-firing heat treatment was investigated, and the following results were obtained. Softening of the multi-purpose Ag-Pd-Zn-In-Sn alloy during porcelain firing simulation was suppressed by controlling the cooling rate. When the cooling rate was adjusted to stage 0(firing chamber moves immediately to upper end position), the alloy was softened during porcelain firing simulation, and the hardness was greatly increased by the additional post-firing heat treatment. When the cooling rate was adjusted to stage 3(firing chamber remains closed), the alloy was not softened even after porcelain firing simulation, and the hardness was apparently lowered by the additional post-firing heat treatment. The apparent increase in hardness in the post-firing heat treated alloy after porcelain firing simulation at cooling rate of stage 0 attributed to the active precipitation. The apparent decrease in hardness in the post-firing heat treated alloy after porcelain firing simulation at cooling rate of stage 3 attributed to the fact that the precipitates were solutionized into the matrix by the post-firing heat treatment.

• Journal of the korean academy of Pediatric Dentistry
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• v.46 no.1
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• pp.64-75
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• 2019

The purpose of this study was to obtain instructions for size selection of prefabricated crown and tooth reduction by 3-dimensional analysis of the size and shape of the maxillary primary central and lateral incisors and prefabricated crowns (celluloid strip, resin veneered stainless steel, and zirconia crowns). The maxillary primary central and lateral incisors of 300 Korean children was scanned with three types of prefabricated crown to create standard three-dimensional tooth models and prefabricated crowns. The shapes of the prefabricated crowns and natural teeth were compared according to four parameters (mesio-distal width, height, labio-palatal width, and labial surface curvature coefficient) and calculated the amount of tooth reduction required for each prefabricated crown. The size 2 resin veneered stainless steel crown, size 1 zirconia crown, and size 2 celluloid strip crown were most similar in shape to the primary central incisor. The size 3 rein veneered stainless steel crown, size 2 zirconia crown, and size 3 celluloid strip crown were most similar to the primary lateral incisor. The amount of tooth reduction was similar in both maxillary primary central and lateral incisors. The incisal reduction was greatest for the zirconia crown. At the proximal surface, the zirconia and celluloid strip crowns required a similar amount of tooth reduction, but more than the resin veneered stainless steel crown. The labial surface reduction was greatest for the zirconia crown. The degree of lingual surface reduction was not significant among the three prefabricated crowns. Among the assessment parameters, mesio-distal crown width was the most important for choosing a prefabricated crown closest to the actual size of the natural crown.