• The Journal of Advanced Prosthodontics
• /
• v.12 no.3
• /
• pp.140-149
• /
• 2020

PURPOSE. This study evaluated the color stabilities of two computer-aided design and computer-aided manufacturing (CAD/CAM) blocks and a nanofill composite resin and the microtensile bond strength (µTBS) between the materials. MATERIALS AND METHODS. Twelve specimens of 4 mm height were prepared for both Lava Ultimate (L) and Vita Enamic (E) CAD/CAM blocks. Half of the specimens were thermocycled (10,000 cycle, 5° to 55℃) for each material. Both thermocycled and non-thermocycled specimens were surface treated with one of the three different methods (Er,Cr:YSGG laser, bur, or control). For each surface treatment group, one of the thermocycled and one of non-thermocycled specimens were restored using silane (Ceramic Primer II), universal adhesive (Single Bond Universal), and nanofill composite resin of 4-mm height (Filtek Ultimate). The other specimens were restored with the same procedure without using silane. For each group, 1 × 1 × 8 mm bar specimens were prepared using a microcutting device. Bar specimens were thermocycled (10,000 cycle, 5° to 55℃) and microtensile tests were performed. Staining of the materials in coffee solution was also compared using a spectrophotometer. Data were analyzed using one-way ANOVA, t-test and post-hoc Scheffe tests. RESULTS. µTBS were found similar between the thermocycled and non-thermocycled groups (P>.05). The highest µTBS (20.818 MPa) was found in the non-thermocycled, bur-ground, silane-applied E group. Silane increased µTBS at some E groups (P<.05). Composite resin specimens showed more staining than CAD/CAM blocks (P<.05). CONCLUSION. CAD/CAM blocks can be repaired with composite resins after proper surface treatments. Using silane is recommended in repair process. Color differences may be shown between CAD/CAM blocks and the nanofill composite after a certain time period.

• Korean Journal of Human Ecology
• /
• v.9 no.3
• /
• pp.297-315
• /
• 2000

The purpose of this study is to provide the basic data for the leisure space planning desirable for adolescents through survey on their using leisure space. Four hundred sixty-six middle and high school students living in Chongju city, Gwesan-gun and Eumsung-gun responded the first basic questionnaire and 160 students among them answered again the second questionnaire for more information on the site of leisure space they want. Frequency, percentage, $x^2-test$ and Multi-Dimensional Scale were methods of analysis. The results are as follows. Adolescents are wasting their leisure time because of insufficient facilities for productive activities. They use the time, when observed in one week, roaming around downtown, studying in off-school academies, visiting shops and playing in the game rooms. And when observed in a month, they use time meeting friends in coffee shops, visiting restaurants, studying in the libraries, playing in the ground and visiting sports facilities. Adolescents' leisure time were different according to sex, age, father's educational level, mother's occupation, household income, and living area. Students hoped the leisure spares to be located in the neighborhood where they can access easily, and facilities they wanted were small shop-buildings, game rooms, off-school academies, schools, sports facilities, studying moms and libraries. It is necessary that adolescents have opportunities to learn how to use their leisure time healthy in the leisure space. And consideration on adolescents living in the remote rural area have to be dealt importantly in the beginning of various planning.

• Resources Recycling
• /
• v.30 no.4
• /
• pp.46-53
• /
• 2021

Biomass can be considered as chemical energy obtained from nature, and includes all living organisms such as plants, animals, and microorganisms. Biomass is eco-friendly, is easily obtainable from the environment, and can be recycled without special treatment processes. Biomass can also be converted into bioenergy fuel through pyrolysis and fermentation. Therefore, it has been considered as a renewable energy source, which prevents the depletion of natural resources such as fossil fuels. In this study, torrefaction to increase the carbon content in various types of biomass sources (sawdust, rice straw, rice bristles, coffee ground, and waste wood) was conducted under an inert atmosphere and at a temperature of 523~573K. The possibility of using torrefied biomass as an alternative to solid fuel for industrial purposes was analyzed by examining the carbon concentration and combustion behaviors.

• Research in Community and Public Health Nursing
• /
• v.14 no.3
• /
• pp.507-519
• /
• 2003

Purpose: The purpose of this study was to identify the prevalence, health behaviors, and control of hypertension in rural areas in Korea. Method: A total of 927 subjects above age 20 were selected from the areas which fell under the jurisdiction of the 24 Community Health Center located in Chungcheongbuk-do. The employees in the Community Health Center visited and interviewed patients. Data were collected using a questionnaire from July to October 2002. Result: The result showed that women had higher hypertension prevalence rates than men and the increment of its rate leveled up according to age. The hypertension prevalence rate was significantly high when the monthly income was less than 1 million won, their type of the Medical Insurance was the Guardian, they were only able to read Korean characters, and they were bereaved of spouses. In the Health behavior related to hypertension, the hypertension group showed a significantly lower level than the non- hypertension group in terms of drinking rate, smoking rate, intake of salt and intake of meat. There was no significant difference in the exercise rate and coffee intake rate between these groups. In the degree of the obesity the hypertension group was significantly higher than the non-hypertension group. The factors related to hypertension were that the duration for the incidence of hypertension was 12 to 60 months and took up 41.2%. The places where the medical check-ups occurred were the Community Health Center at 46.6%, the medical institution was mostly hospitals recording 46.5%. There were 66.1% of the targets who knew well about their blood pressure and there were 64.7% people who received education about it. As for the education place, the rate of Community Health Center was mostly high and it stood at 77.0%. In the aspect of the management of hypertension, the targets who took medicine on a regular basis were up to 76.1% and the targets who measured blood pressure once a month happened to be about 46.1 %. The targets who always recorded their blood pressure were 3.8%, chest X-ray as a related examination of hypertension reached 32.6%, electrocardiogram examination was 36.2%, cholesterol and serum lipid examination took up 33.6%, and the eye ground examination took 7.3%, which showed the lowest level of all.