• Restorative Dentistry and Endodontics
• /
• v.24 no.3
• /
• pp.465-472
• /
• 1999

The aim of this study was to determine the shear bond properties of four dentin bonding systems to internal cervical dentin, and to investigate the effect of the pretreatment for removing smear layer and position of dentin on shear bond strength of dentin bonding agents. The materials tested in this study were consisted of four commercially available dentin bonding systems[Allbond 2(AB), Clearfil Linerbond 2(CL), Optibond FL(OP), Scotchbond Multi-purpose(SB)], a restorative light-cured composite resin[Z100]J and a chelating agent[RC-prep(RC)]. Fifty-six freshly extracted human molars were used in this study. Dentin specimens were prepared by first cutting the root of the tooth 1mm below the cementoenamel junction with a diamond bur in a high speed handpiece under air-water coolant, and then removing occlusal part at pulp horn level by means of a second parallel section, The root canal areas were exposed by means of cutting the dent in specimens perpendicular to the root axis. Dentin specimens were randomly assigned to two groups(pretreated group, not-pretreated group) based on the pretreatment method of dentin surface. In pretreated group, RC was applied to dentin surface for 1minute and then rinsed with NaOCl. In not-pretreated group, dentin surface was rinsed with saline Each groups were subdevided into four groups according to dentin bonding systems. Four dentin bonding systems and a restorative resin were applied according to the directions of manufacturer. The dentin-resin specimens were embedded in a cold cure acrylic resin, and were cut with a low speed diamond saw to the dimension of $1{\times}1mm$. The cut specimens were divided into three groups according to the position of internal cervical dentin. The shear bond properties of dentin-resin specimens were measured with Universal testing machine (Zwick, 020, Germany) with the cross head speed of 0.5mm/min. From this experiment. the following results were obtained : 1. In case of shear bond strength, there was no significant difference among dentin bonding systems in not-pretreated groups, whereas in pretreated groups, the shear bond strengths of AB and of SB were statistically significantly higher than those of CL and of OP. 2. The shear bond strengths of AB and of SB in pretreated groups were significantly higher than those in not-pretreated groups. 3. The shear bond strengths of radicular layer of OP were higher than those of occlusal layer of OP in not-pretreated groups, and of AB in pretreated groups. The shear bond strengths of radicular layer of AB and of CL in not-pretreated groups were higher than those in pretreated group.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2009.05a
• /
• pp.310-313
• /
• 2009

Several high nitrogen stainless steel ingots(100kg) were fabricated with changing Ni and $[N]_2$ contents by Pressurized Vacuum Induction Melting(P_VIM). After free forging process, chemical compositions, microstructure and mechanical properties were estimated. Hardness was increased with the increase of $[N]_2$ content. Furthermore, microstructure including a lot of tempering twins was observed with optical microscope. Mechanical properties were estimated as function of solution treatment temperature and cooling method(air/water) under duration time of 1 hr on sample that were fabricated with Ni content under the atmospheric $[N]_2$ pressure. At solution treatment range of $1050{\sim}1100^{\circ}C$, hardness was decreased with the increase of solution temperature and there were little discrepancy of microstructure and hardness with cooling method. Computer simulation was carried out in order to inspect pass schedule in cold rolling process. When the condition of simulation was roll speed of 2.5mpm, rolling rate $15{\sim}17%$ per pass, it was ascertained that the formation such as deformation by sticking and lamellar sliver etc. was restricted from a simulation.

• Journal of Korean Society of societal Security
• /
• v.4 no.2
• /
• pp.65-72
• /
• 2011

This study was carried out to investigate the cause of acidification of rainwater and to evaluate the possibility of alternative water resource in Saemangeum. The rainwater were collected in the kwangwhal-myun, Saemangeum from March to September, 2009. The collected 7 samples were analyzed with pH meter, IC (ion chromatography) and ICP (inductively coupled plasma) about the pH and the major ions ($SO{_4}^{2-}$, $NO_3{^-}$, $Cl^-$, $Ca^{2+}$, $K^+$, $NH^{4+}$, $Na^+$ and $Mg^{2+}$) of rainwater. The order of the major anion concentration and the acidification contribution in the rainwater was $SO{_4}^{2-}$>$NO_3{^-}$>$Cl^-$, and that of the major cation was $Ca^{2+}$>$K^+$>$NH_4{^+}$>$Na^+$>$Mg^{2+}$. In the initial rainwater, the major ions concentration were higher than the middle period. pH of the rainwater was the lowest at May, but similar to the results of the others. And pH of the rainwater were significant correlation with $SO{_4}^{2-}$ and $Cl^-$ in Saemangeum. From this results, the rainwater was slight acidic, and $SO{_4}^{2-}$ was the main factor contributed to the rainwater acidification in Saemangeum.

• Korean Journal of Food Science and Technology
• /
• v.29 no.5
• /
• pp.963-968
• /
• 1997

Cereals and legumes were ground, blended and extruded with a twin-screw extruder to form a reconstituted grain. The basic formula was as follows: brown rice 30%, barley 30%, wheat 20%, millet 5%, sorghum 5%, soybean 7%, and red bean 3%. Extrusion conditions were properly set for feed moisture content of $24{\sim}30%$, barrel temperature of $50{\sim}60^{\circ}C$, and screw speed at 250 rpm. The extruded grain was air-dried and evaluated for quality characteristics, compared with milled rice. Size and shape of the reconstituted grain were similar to short-grain milled rice. Stacking volume of the reconstituted grain was a little higher than that of milled rice, and its water absorption was more rapid. From the texture measurements, hardness of cooked reconstituted grain was slightly lower and adhesiveness was appeared to be higher.

• Journal of Wetlands Research
• /
• v.16 no.3
• /
• pp.423-429
• /
• 2014

Due to high imperviousness rates of the roads, various pollutants originated from vehicle activities and air depositions are accumulated on the road surfaces. The washed-off pollutants can deteriorate the water quality and destroy the aqua-ecosystems with their toxicity. Usually the roads are paved with asphalt and concrete, which can affect on the pollutant concentrations with different frictional forces. Therefore, this research is performed to evaluate the influences of different pavement type on discharged concentrations of pollutant. The results shows the first flush phenomenon was occurred on both pavement types. However, peak concentrations are higher in concrete pavement areas than asphalt pavement because concrete pavement has high contact area with vehicles. The EMCs(Event Mean Concentration) also shows high values in concrete paved roads. As a result of this research, it can be concluded the pavement type is also one of the important affecting factors on pollutant emissions from the roads.

• Atmosphere
• /
• v.29 no.5
• /
• pp.511-523
• /
• 2019

A new Korean Meteorological Administration (KMA) airborne measurement platform has been established for regular observations for scientific purpose over South Korea since late 2017. CRDS G-2401m analyzer mounted on the King Air 350HW was used to continuous measurement of CO₂, CH₄ and CO mole fraction. The total uncertainty of measurements was estimated to be 0.07 ppm for CO₂, 0.5 ppb for CH₄, and 4.2 ppb for CO by combination of instrument precision, repeatability test simulated in-flight condition and water vapor correction uncertainty. The airborne vertical profile measurements were performed at a regional Global Atmosphere Watch (GAW) Anmyeon-do (AMY) station that belongs to the Total Carbon Column Observing Network (TCCON) and provides concurrent observations to the Greenhouse Gases Observing Satellite (GOSAT) overpasses. The vertical profile of CO₂ shows clear altitude gradient, while the CH₄ shows non-homogenous pattern in the free troposphere over Anmyeon-do. Vertically averaged CO₂ at the altitude between 1.5 and 8.0km are lower than AMY surface background value about 7 ppm but higher than that observed in free troposphere of western pacific region about 4 ppm, respectively. CH₄ shows lower level than those from ground GAW stations, comparable with flask airborne data that was taken in the western pacific region. Furthermore, this study shows that the combination of CH₄ distribution in free troposphere and trajectory analysis, taking account of convective mixing, is a useful tool in investigating CH₄ transport processes from tropical region to Korean region in winter season.

• Journal of Korean Society of Environmental Engineers
• /
• v.31 no.10
• /
• pp.901-908
• /
• 2009

We examine the processing method of the food wastewater to direct spray at living waste incinerator. The demoscale stoker system is used as a incineration facility. The results show that it brings effect on the reduction of nitrogen oxide ($NO_x$) concentration as well as the ammonia ($NH_3$) amount in SNCR (selective non-catalytic reduction) by the incineration of food wastewater which is containing a plentiful ammoniac nitrogen ($NH_3$-N). Furthermore, the stability of incineration facility and the extension of operation period is actualized as a improvement of clogging phenomenon on outer wall of water pipe as the 870~$950^{\circ}C$ maintain of exit temperature in a second combustor by spray of the food wastewater. The 26 items of air pollution matter of nitrogen oxide ($NO_x$), sulfur oxide ($SO_x$) and dioxin etc. are measured. The results show that it is under the value of allowable exhaust standard.

• Journal of Korean Society of Environmental Engineers
• /
• v.31 no.2
• /
• pp.132-138
• /
• 2009

The energy efficiency and environment-friendly aspect of the railway system would be superior to other on-land transportation systems. In a preliminary feasibility study stage and selection of optimal railway corridor, the energy efficiency and problems related to environment are usually not considered. For the selection of optimal railway corridor, geographical features and facility of management are generally considered. Environment effect factors for the selection of environment-friendly railway corridor are focused and studied in this paper. In this study, various analysis of opinion of specialists (railway, environment, transport, urban planning, survey) and the guideline for construction of environment-friendly railway were accomplished. From these results of various analysis, 7 major categories (topography/geology, flora and fauna, Nature Property, air quality, water quality, noise/vibration, visual impact/cultural assets) were extracted. To select environment friendly railway corridors, many alternatives should be compared optimal corridor must be selected by a comprehensive assessment considering these 7 categories. The investment for railway systems can be encouraged by the considering of main environmental effect factor evaluated with the modified environmental weight factors for environment-friendly railway construction.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.17 no.2
• /
• pp.101-109
• /
• 2013

Recently, it is certain that the increase of heating and cooling energy consumption by radical change in climate condition has caused serious problems related to environmental and energy concerns associated with increase of fossil fuel usage and carbon dioxide production as well as global warming. So, various actions to reduce greenhouse gas exhaustion and energy consumption have been prepared by world developed countries. Our government has also been trying to seek energy control methods for houses and buildings by proclaiming political polices on low-carbon green growth and construction and performance standards for environment-friendly housing. The energy consumption by buildings approximately reaches 25% of total korea energy consumption, and the increasing rate of energy consumption by buildings is stiffer than the rate by the other industries. The greatest part in the buildings of the energy consumption is building facade. While lots of research projects for reducing energy consumption of the facade have been conducted, but a few research projects on concrete comprising more than 70% of outsider of buildings has been tried. This research presents here a study to improve the insulation property of structural concrete formed by micro form admixture (MFA) with experimentally reviewing the physical, mechanical and thermal characteristics of the concrete. As the results of this experiment, in the case of concrete mixed with MFA, slump loss has been improved. As the mixing ratio of MFA increases, the compressive strength is decreased and thermal conductivity is increased. Also it was found that water-cement ratio increases, the compressive strength is decreased and thermal conductivity is increased. but, there was not big influence by the change of fine aggregate ratio.

• Korean Journal of Food Science and Technology
• /
• v.30 no.3
• /
• pp.542-547
• /
• 1998

In order to study bread properties utilizing extracts of pine needle, various mixing percentage were applied to select appropriate ratio between water and extracts. Dough pH, dough pH after first fermentation, dough volume, bread volume and baking loss rate were tested to investigate bread properties after adding extracts of pine needle to bread. The results were summarized as follows; The effects of extracts percentage on pH value of dough according to preparation method were the lowest in the method of hot air drying of pine needle powder. After first fermentation, dough pH was tended to have a the same tendency as above. Dough volume and bread volume were tended to be increased as extracts percentage of pine needle were increased. The percentage of baking loss tended to be a little increased as addition level of extracts was increased. Strength of hardness were increased as storage time passed away. In conclusion, the taste and texture of bread were tended to be decreased as storage time goes, but the strength of pine needle flavour were tended to be increased as addition level of extracts were increased, irrespective of preparation method.