• Journal of Technologic Dentistry
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• v.22 no.1
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• pp.145-152
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• 2000

In order to select an effective antibiotic substance against oral resident bacteria, we were isolated from soil and texonomically analyzed. Seven hundred and eighteen strains were isolated on humic acid- vitamin agar(HV agar) and 220 strains were on methanol medium from three each paddy forest, field and riverside soil samples. So, during the screening of antibiotics from soil, we isolated microorganisms showing powerful antagonistic activity against oral resident bacteria. Microorganism was tested against 25 strains of bacteria, yeast and fungi. Among them, No. 248 strain exhibited the most strongly growth inhibition. So, the taxonomical analysis the isolated strain was found to be unknown Actinomyces sp. and was named No 248. A production of the antibiotics from No. 248 begins at the early exponential phase developed at the 72th hour under the optinum conditions. The property of No. 248 antimicrobial compound was very stable under acid(pH 3.0) and alkali(pH 10.0) treatment, but it was instable in heat treatment at $120^{\circ}C$. For the improvement of antibiotic activity, two mutants were isolated from strain No. 248 by the treatment of mutagenic agents, NTG and hydroxylamine. As a result, the mutant strains excreted the potent antibiotics to inhibit the growth of Candida albicans.

• Journal of Technologic Dentistry
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• v.28 no.1
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• pp.27-41
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• 2006

The physical property and phase transformation in a commercial dental casting high gold alloy was investigated as a function of ageing temperature and time using microvickers hardness tester, X-ray diffraction, optical and electron microscopy and EPMA analyser. 1. With increasing ageing time, the hardness of solution-treated gold alloys increased slowly at the initial stage of ageing treatment at an ageing temperature of $300{\sim}400^{\circ}C$, and it reached a maximum value of hardness at the medium stage. Finally, it decreased gradually during further ageing. The maximum value of hardness at was similar with that of the conventional materials and suitable for using as the crown & bridge. 2. During isothermal ageing at a temperature range of $300{\sim}400^{\circ}C$, three phases consisting of the Au-rich ${\alpha}_1$phase with a face-centered cubic structure, the Pt3Zn ${\alpha}_2$phase with an ordered AuCu3(L12) type(f.c.c.) and the Pt-rich ${\alpha}_3$phase with face-centered cubic structure in solution-treated gold alloys were transformed into different three phases consisting of the ${\alpha}_1$phase, the ${\alpha}_3$phase and the PtZn $\beta$phase with an ordered AuCu I(L10) type. 3. The hardening of gold alloys was attributed to the lattice strains of the matrix resulting from the transformation of the ${\alpha}_2$phase to the $\beta$phase. 4. The softening of gold alloys during over-ageing was attributed to the coarsening of the nodules consisting of the $\beta$phase and ${\alpha}_1$matrix.

• Journal of Technologic Dentistry
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• v.32 no.3
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• pp.241-253
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• 2010

Purpose: The purpose of this study was to analyze the career barriers of students studying dental technology in D-College. Methods: This study targeted 490 college students studying Dental Technology in D-College. The survey about career barriers on this study consisted of 45 questions and was scored with 5-points per question. The corrected data was analyzed by SAS V8 for Windows. Results: The difference analysis of career barriers shows that differences exist depending on gender(p<.01) and serving military service(p<.05). Especially, female students(2.69) and male students(2.65) who didn't serve the military are more susceptible to career barriers. In the sub factors of career barriers, differences exist depending on and in order of gender, serving military service, experience studying one more year to enter the college, day and night, the affiliation of highschool graduated from, and hometown. The correlation between the sub factors of career barriers and perception of career barriers manifested 'Lack of self assurance'(0.84), 'Sense of physical inferiority'(0.76), 'Relationship with other important people'(0.73) and 'Lack of information on occupation' in order. Conclusion: In the factors affecting non-decision on the career, 'Lack of self assurance'(=0.2465) is the highest in terms of influence, followed by 'Difficulty in interpersonal relations’(=0.1801) and 'Lack of information on occupation' (=0.1391).

• Journal of Technologic Dentistry
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• v.33 no.4
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• pp.479-493
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• 2011

Purpose: The career education of the college student needs a new awareness. This research provides fundamental data from analyzing necessities of student's career education according to plans of a career education. Methods: Make use of SAS 8.0 of windows and descriptive statistics analysis on investigate Dental Technology 570 students in Daegu. And also it analyzes difference of ispectable t-test and ANOVA. Results: According to a gender, a job experience, where they are come from, there is a meaningful difference of an information and an entrance motive for choosing a major (<.05). The time of choosing the major are different meaningfully (<.001). An awareness about the method of a career achievement is a meaningful difference between men and women(<.05). As getting old, the method of a career achievement is higher and there are meaningful differences according to a grade, job experience and a entrance screening(<.01). In accordance with a gender, a grade, entrance screening, there are meaningful differences of a degree for obtaining the career information activities(<.01). In accordance with an age, when they choose a major, there is a difference(<.001). In accordance with a gender and a age, there are meaningful differences of a career plan(<.001). The age difference is slight. In accordance with a gender and a age, there are meaningful differences how to effort for the career(<.001), and also according to an entrance screening, an entrance motive(<.05). These mean that the first priority for choosing the career and going into the world is a school record. There are meaningful differences of people that the student choose for consulting the career(<.01). According to the job experience there are meaningful differences(<.001). Conclusion: By investigating and analysing the student's career plan, we need to seek how students choose their career reasonably and desirably. And also we need to teach a career education systematically.

• Journal of Technologic Dentistry
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• v.30 no.2
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• pp.93-103
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• 2008

This research is designed for a consumer, not a supplier when it was designed. And the purpose is to present the reference data which is in order to improve the curriculum by analyzing the present subject of the curriculum. The research collected the curriculum for Dental Technology from a total of 20 schools --3-year colleges and 4-year colleges-- all in Korea. And we analyzed the average credits of subjects from students. As a result of this analysis, we get the conclusion below: 1. In a distribution which students answered about each subjects; Dental esthetic, Dental morphology I II, Dental morphology practice I II, and Seminar don't have many credits and mostly have a converged tendency in high points, according to the arithmetic mean of the major basis subjects. 2. In an analysis of the correlation which is based on the distinction of sex; Dental ceramics practice III, Medical terminology, Seminar, and The major basis subjects have a meaningful difference. (${\rho}$ < 0.05) 3. In an analysis of the correlation which is based on an age; The major basis subjects, and the application subjects have meaningful difference. (${\rho}$ < 0.05) 4. In a correlation coefficient between subjects; The correlation coefficient of the major application subjects is higher than the major basis subjects. According to the student ? t, we found that the level of significance is ${\rho}$ < 0.001, which is meaningful. We feel that Department of Dental Technology also highly need to design, and conduct focusing on a consumer who is working at the society, not a supplier. And we need to increase or decrease credits which have a meaningful difference.

• Journal of Technologic Dentistry
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• v.29 no.2
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• pp.49-64
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• 2007

This research collected the curriculum for Dental Technology from a total of 20 schools -3-year colleges and 4-year colleges- all in Korea. And we analyzed the average credits of subjects from students. As a result of this analysis, we get the conclusion below: 1. In a distribution which students answered about each subjects; Seminar, Dental morphology I II, Dental morphology practice I II, and Dental devices & instruments don't have many credits and mostly have a converged tendency in high points, according to the arithmetic mean of the major basis subjects. 2. In an analysis of the correlation which is based on the distinction of sex: Complete denture prosthodontics I II III, Dental orthodontics I II, Dental orthodontics practice I II, and Dental orthodontics & practice III have a meaningful difference. ($\rho$< 0.05 ) 3. In an analysis of the correlation which is based on an age The major basis subjects -Introduction to dental technology, Dental esthetic, and Dental casting procedure-, and the major application subjects -Crown and bridge prosthodontics practice, Complete denture prosthodontics, Dental orthodontics, Dental orthodontics practice, and Operative dentistry laboratory technology- have meaningful difference. ($\rho$< 0.05 ) 4. In a correlation coefficient between subjects; The correlation coefficient of the major application subjects is higher than the major basis subjects. According to the student - t, we found that the level of significance is $\rho$< 0.001, which is meaningful. We feel the lack of a limitation which we didn't survey all students who are major in Department of Dental Technology. And we also feel that we'd better to consider not only students who being in college but also graduated students.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.5
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• pp.471-479
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• 2010

The adiabatic two-phase flow in single rectangular microchannels was studied for different aspect ratios. The working fluids were liquid water and nitrogen gas. The hydraulic diameters of the rectangular microchannels were 490, 322, and $143\;{\mu}m$, and the widths of the microchannels were around $500\;{\mu}m$. The two-phase flow pattern was visualized using a high-speed camera and a long-distance microscope. This study was focused on bubble flow regimes. From the visualized images, the bubble velocity, bubble length, number of bubbles, and void fraction were evaluated. Further, the pressure drop in a single bubble was evaluated by using a unit cell model. The bubble velocity is proportional to the superficial velocity. Further, the relationship between the void fraction and the volumetric quality is linear. The pressure drop in a single elongated bubble is strongly related to the aspect ratio. Finally, the new correlation about the pressure drop of a single elongated bubble in the rectangular microchannel was proposed.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.33 no.2
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• pp.201-204
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• 1988

To find out the relationship between the eco-physiological characteristics and wind damage of rice leaves by typhoon 'Thelma' occurred at young panicle formation stage of rice plant, the study was carried out. The rate of dead leaves by wind damage in Indica X Japonica varieties were higher than that in Jap. varieties. Ind. X Jap. varieties which had erect and broader leaves had the higher number of silicified cell, moisture loss and stomatal aperture in leaves. And the wind damage were positvely correlated with the characteristics such as the number of silicified cell (r=0.7546$\^$*/), rate of moisture loss (r=0.8343$\^$**/) and stomatal aperture (r=0.8460$\^$**/) of rice leaf blade etc.

• Journal of Technologic Dentistry
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• v.28 no.2
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• pp.399-415
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• 2006

This research collected the curriculum for Dental Technology from a total of 20 schools-eighteen 3-year colleges and two 4-year colleges all in Korea. We divided 4 groups as regions from 20 colleges, and we compared the credit of university students who finished all the required courses and want to apply for a national examination and the credit to be had from another educational institution. As a result of this analysis, we get the conclusion below: 1. In the curriculum, average credit are shown like this order: Science of Dental materials 5.45 Orthodontics Technology 4.10 Dental Morphology 3.80 Oral Anatomy 3.05 Dental Health Science 2.45 Public Health Science 2.40 These show that the credit of fundamental studies, which is in order to take Dental Prosthetics, is increased. 2. In the curriculum, average credit are shown like this order: Crown and Bridge Technology 7.25 Removable Partial Dentures Technology 6.55 Complete Dentures Technology 6.40 Dental Ceramics 4.95 Inlay Technology 2.30 3. In the curriculum, average credit are shown like this order: Crown and Bridge Technology(Lab) 5.90 Removable Partial Dentures Technology(Lab) 5.35 Complete Dentures Technology(Lab) 5.30 Dental Ceramics(Lab) 4.35 Average points between regions in the subject of a national written exam are mostly similar, but the deviation among Science of Dental Materials, Crown and Bridge Technology, Removable Partial Dentures Technology, and Complete Dentures Technology is large. And in the practical technique exam, the deviation among Crown and Bridge Technology(Lab), Removable Partial Dentures Technology(Lab), and Complete Dentures Technology(Lab) is great.

• Journal of Technologic Dentistry
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• v.40 no.1
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• pp.33-40
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• 2018

Purpose: The purpose of this study was to investigate the influence of mechanical properties of various ultra-dental stone by setting methods. Methods: 240 cylinder specimens($10mm{\times}20mm$) were prepared from three ultra-dental stones(Gemma, Die keen and Fuji rock; n = 80) in accordance with the manufacturers' recommendations. Half of the specimens of each stone(n = 40) were dried in open air within a room temperature; the other half(n = 40) underwent in a silicone rubber mold in open air for 30 minutes and then were dried in a microwave oven for 10 minutes to 600W. Compressive strength(CS), compressive modulus(CM) and diametral tensile strength(DTS) conducted until fracture using Instron 5966 at each of the following periods: 1 and 24 hours from mixing. One-way analysis of variance and Scheffe's post hoc test were performed for statistical comparisons at a significance level of P<.05. Results: The CS and CM values in all dental stone indicated highest after 24h(54.25 MPa < ) than the values for specimens dried in microwave method. The DTS values revealed the highest microwave method. However, in 24h, FJ(Fu-ji rock) and GM(Gemma) had lower mechanical properties than air. Conclusion : Within the limitations of this study, CS did not influence by microwave method but DTS affected according to the setting.