• Journal of the korean academy of Pediatric Dentistry
• /
• v.25 no.1
• /
• pp.103-115
• /
• 1998

Adhesion of composite resin to tooth structure has been of tremendous signgicance in clinical dentistry. Due to the lack of adhesion between composite restorative resins and enamel and dentin, microleakage occurs at the tooth/restoration interface. This may lead to discoloration, secondary caries, marginal breakdown, postoperative sensitivity, and even pulpal pathology. According to extensive use of composite resin, every effort on improving bonding strength and reducing microleakage between a tooth and composite resin has been continued. This study was conducted to determine the difference in microleakage in enamel and dentin treated with air-abrasion, acid etching and combination when restored with composite resin. Class V cavities were prepared on 30 premolars. The specimens were divided into following groups. group 1:air-abrasion+Scotchbond Multi-purpose group 4 :air-abrasion+All-Bond 2 group 2:acid etching+Scotchbond Multi-purpose group 5 :acid etching+All-Bond 2 group 3:combination+Scotchbond Multi-purpose group 6 :combination+All-Bond 2 #combination:air-abrasion + acid etching The specimens were filled with Z-100 after application of Scotchbond Multi-purpose and All-Bond 2. Thermocycling was conducted by alternately dipping the specimens in $5^{\circ}C$ and $55^{\circ}C$ water for 30 seconds 500 times. 1% methylene blue was applied and the specimens were left for 24 hours at $37^{\circ}C$. After washing out the dye, the tooth was sectioned buccolingually along the axis. The sectioned surface was observed with stereoscope for dye penetration. The author has measured the microleakage in teeth prepared with air-abrasion, acid ethching and combination to study the difference in microleakage following different methods of tooth surface treatment and has come to following results. 1. In comparing microleakage between groups, group 1 and 4 showed statistically significant difference from group 2, 3, 5 and 6(p<0.05). There was no significant difference among group 2, 3, 5, 6(p>0.05) nor between group 1 and 4(p>0.05). 2. In comparing microleakage among tooth surface treatment methods, Air-abrasion group showed significantly more microleakage than acid etching group and combination(airabrasion + acid etching) group(p<0.05). Combination(acid etching+air-abrasion)group tended to show lesser microleakage than acid etching group, but this was not statistically significant(p>0.05). 3. In comparing microleakage between bonding agents, there was no statistically significant difference between Scotch bond Multi-purpose and All-Bond 2(p>0.05).

• Fire Science and Engineering
• /
• v.18 no.3
• /
• pp.95-102
• /
• 2004

This paper has analyzed compressed air-breathing that fire fighters use in Korea. And the local and the foreign standards for compressed air have been compared. Through the survey, it has been found that over 75% of all the respondents have ever had simple abnormal symptoms after wearing air respirators, and among the abnormal symptoms, nausea and headache are most frequent. Maintenance and exchange of compressor filters were poor and it can be another cause of abnormal symptom of fire fighters. Korea does'nt have any particular standards for compressed air-breathing, and the compressed air that is used by fire fighters is not different from air for industrial use. However, advanced countries like Europe, Canada and America, they have special standards for compressed air-breathing that fire fighters use. Through the analysis of components of the compressed air used in Korea, it has been found that all the samples have more water than the international standards.

• Proceeding of Spring/Autumn Annual Conference of KHA
• /
• 2006.11a
• /
• pp.291-296
• /
• 2006

The purpose of this study were to make clear the present condition of indoor thermal and air environment by air-conditioning in school classrooms and to analyze the relation of the living conditions with indoor environment. The measurements on physical elements and observations on living conditions were carried out in 6 classrooms of 3 middle or high schools. Measuring elements were indoor temperature, relative humidity, $PM_{10}$ and $CO_2$ concentration. As results, the averages of indoor temperature each classrooms were 24.9${\sim}$26.6 . Most of classrooms were lower than the Maintenance standard(26${\sim}$28 ) of School Health Law. The means of relative humidity were 51.3${\sim}$72%, all classrooms were ranged within the standard(30${\sim}$80%). The means of $PM_{10}$ concentration were 3.5${\sim}$23.1 ${\mu}g/m^3$, all classrooms were kept within the standard(100 ${\mu}g/m^3$). The means of $CO_2$ concentration were 1218.7${\sim}$4705.4 ppm, all classrooms were exceed the standard(1,000ppm). The results of analysis on relations of living conditions with the physical elements are as follow; the air conditioner set of temperature, windows and doors opening elapsed time, the number of students in classrooms and activities of students had certain effect on indoor environment.

• Journal of Environmental Health Sciences
• /
• v.26 no.3
• /
• pp.32-37
• /
• 2000

Nowadays, a new word called SBS(sick building syndrome) has been come into existence. At the point of time when an interest about indoor air pollution and, according to this, countermeasure plan are internationally. Moreover institutional countermeasure should be attended at national level since indoor air quality in public places where many people gather is directly connected with national health. Especially indoor pollution of indoor stadia where all sorts of sports are held can give rise to every kinds of respiratory ailments to players as well as audiences. So it is presented as a main factor that indoor space of stadia is crowded with players and audiences compared with other kinds of indoor space. Therefore, in this research to analyze pollution degree of indoor circumstance for gymnasium and exercising room of folk wrestling. basketball, judo, wrestling, hapkido, swordsmanship and boxing making indoor gymnasium and exercising room an object, when 7 items were measures such as thermocircumstance(temperature, relative humidity, air current, intensity of illumination), dust, carbon monoxide, and carbon dioxide being based on the indoor environmental standard of the first clause of Article 45 of public utilization service which is showed at public hygiene of the Ministry of Health and Social Affairs, it was showed that indoor temperature, relative humidity, air current and intensity of illumination were over standard amount at the most of folk wrestling gymnasium and exercising room. Indoor density of carbon monoxide was preserved to the extent of standard amount (10ppm) at all gymnasiums but carbon dioxide was not in excess of standard amount(1,000 ppm) at most of gymnasiums. Indoor density of dust induced from respiration exceeded the standard amount (150 $\mu\textrm{g}$/㎥) at all gymnasiums of the folk wrestling. Since the folk wrestling players and participants feel physical subjective symptom seriously, in other words the degree of indoor air pollution at gymnasiums and exercising rooms of the folk wrestling is very high, fundamental solution and countermeasure plan should be presented.

• Restorative Dentistry and Endodontics
• /
• v.38 no.2
• /
• pp.73-78
• /
• 2013

Objectives: This study evaluated the effect of three different air-drying times on microleakage of three self-etch adhesive systems. Materials and Methods: Class I cavities were prepared for 108 extracted sound human premolars. The teeth were divided into three main groups based on three different adhesives: Opti Bond All in One (OBAO), Clearfil $S^3$ Bond (CSB), Bond Force (BF). Each main group divided into three subgroups regarding the air-drying time: without application of air stream, following the manufacturer's instruction, for 10 sec more than manufacturer's instruction. After completion of restorations, specimens were thermocycled and then connected to a fluid filtration system to evaluate microleakage. The data were statistically analyzed using two-way ANOVA and Tukey-test (${\alpha}$ = 0.05). Results: The microleakage of all adhesives decreased when the air-drying time increased from 0 sec to manufacturer's instruction (p < 0.001). The microleakage of BF reached its lowest values after increasing the drying time to 10 sec more than the manufacturer's instruction (p < 0.001). Microleakage of OBAO and CSB was significantly lower compared to BF in all three drying time (p < 0.001). Conclusions: Increasing in air-drying time of adhesive layer in one-step selfetch adhesives caused reduction of microleakage, but the amount of this reduction may be dependent on the adhesive components of self-etch adhesives.

• Journal of Bio-Environment Control
• /
• v.24 no.3
• /
• pp.243-251
• /
• 2015

This study aimed to determine the effects of root zone cooling using air duct on air temperature distribution and root zone and leaf temperatures of sweet pepper (Capsicum annum L. 'Veyron') grown on coir substrate hydroponic system in a greenhouse. When the air duct was laid at the passage adjacent the slab, the direction of air blowing was upstream at $45^{\circ}$. The cooling temperature was set at $20^{\circ}C$ for day and $18^{\circ}C$ for night. For cooing timing treatments, the cooling air was applied at all day (All-day), only night time (5 p.m. to 1 a.m.; Night), or no cooling (Control). The air temperature inside the greenhouse at a height of 40 and 80cm above the floor, and substrate and leaf temperatures, fruit characteristics, and fruit ratio were measured. Under the All-day treatment, the air temperature was decreased about $4.4{\sim}5.1^{\circ}C$ at the height of 40cm and $2.1{\sim}3.1^{\circ}C$ at the height of 80cm. Under the Night treatment, the air temperature was decreased about $3.4{\sim}3.8^{\circ}C$ at the height of 40cm and $2.2{\sim}2.7^{\circ}C$ at the height of 80cm. The daily average temperature in the substrate was in the order of the Control ($27.7^{\circ}C$) > Night ($24.1^{\circ}C$) > All-day ($22.8^{\circ}C$) treatment. Cooling the passage with either upstream blowing at $45^{\circ}$ or horizontal blowing at $180^{\circ}$ was effective in lowering the air temperature at a height of 50cm; however, no difference at a height of 100cm. Cooling the passage with perpendicular direction at $90^{\circ}$ was effective in lowering the air temperature at the height between 100 and 200cm above the floor; however, no effect on the temperature at the height of 50cm. A greater decrease in leaf temperature was found at 7 p.m. than that at 9. a.m. under both All-day and Night treatments. Fresh weight partitioning of fruit was in the order of the All-day (48.6%) > Night (45.6%) > Control (24.4%) treatment. A higher fruit production was observed under the All-day treatment, in which the accumulated average temperature was the lowest, and it may have been led to a higher proportion of photosynthate distributed to fruit than other treatments.

• Journal of Advanced Marine Engineering and Technology
• /
• v.38 no.7
• /
• pp.814-820
• /
• 2014

Due to the development of human civilization, industrialization and urbanization, the human race demanded the food, clothing and shelter as well as a comfortable living environment. For the purpose of this, the refrigeration and air conditioning part was carried out research and development. However, high oil prices and environmental pollution having problems in the 21st century cannot be overlooked. As an alternative, thermal system was designed using the heat pump to applied sea water heat source. In this paper, outside and sea temperatures are analysed in 2010 and carried out the performance analysis simulation at All water and All Air heat pump system by HYSYS program for domestic use. As a result, total average COP of the system is 3.37 from All Water system and All Air is 3.48. It showed that high performance confirmed in both system.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.18 no.12
• /
• pp.999-1006
• /
• 2006

A study of temperature profiles in mixing zone of AHU (air handling unit) can contribute greatly to enhance performance of AHU system, so the study on the temperature distribution between RA (return air) and OA (outdoor air) is important to analyze the mixing characteristics in a mixing zone of AHU. Accordingly, the temperature profiles during RA (return air) and OA (outdoor air) supply process into mixing zone of AHU with an air mixer are studied experimentally. The effect of air mixer, OA temperature and RA/OA flow rate are studied in detail. In this study, the results show that the mixing efficiency is all high for installed the air mixer. The more OA temperature increase and OA flow rate decrease, the more mixing efficiency is high.

• Journal of the Korean housing association
• /
• v.15 no.3
• /
• pp.101-108
• /
• 2004

To find more efficient exhaust effect, air curtain of upward or downward trend in gas table and left or right side of range hood were made. As result that film vapor from range hood lower part by digital camera, the air current change by moving existence and nonexistence of exhaust fan and direction of air curtain were known. Under all experiment condition, upward air curtain superior exhaust performance.

• Journal of Biosystems Engineering
• /
• v.17 no.2
• /
• pp.177-191
• /
• 1992

The MAFSAP(Monitoring and Forecasting System of Air Pollution) was developed to measure the weather and air pollution data automatically, then make them input to microcomputer and analyze them for monitoring and forecasting air pollution at all times. And the air pollution telemetering systems installed at Young-Dong Thermal Power Plant was analyzed and an ideal telemetering system utilizing MAFSAP was suggested.