• Journal of Environmental Health Sciences
• /
• v.4 no.1
• /
• pp.26-33
• /
• 1977

A bacteriological research of the school desks, bags and indoor-shoes was made from Oct. 2, 197 through May 28, 1976. The research included one girl's middle school, two boy's middle schools, two boy's high schools and 15 girl's high schools, alltogether 244 students from 28 schools, The research was analyzed and the results are as follows: 1) The research showed that 95% of the indoor-shoes materials were of cloth. Only 13% of the students carried the indoor-shoes in shoes sacks and 84.8% of them kept the shoes in schoolbags with books and lunchbox. 2) Only 5% of them cleaned their shoes every week and 79% cleaned every six. 3) 49.3% of the students kept the indoor-shoes in the school bag with other contents at home. 4) 88% of the bag was made of vinyl and 24.8% of the students carried their lunch in their bag without lunch box. 5) The research showed that 79.1% of the students never cleaned their bags. 6) In using the desk drawer, 58.2% of the students put their out-door shoes into the drawer, 18.9% of them kept their lunch in it, 11.9% used it keeping books alone and 11% keeping school bags with books. 7) 30.4% of the students had an experience of having cleaned their desks and 69.6% were unconcerned wirh desk-cleaning. 8) 34.4% of the indoor-shoes using school showed fecal coliform positive, 40.2% showed non-fecal coliform positive and 25.4% showed no reaction to IMViC. 9) The 34.4% of the fecal coliform positive showing schools, equivalant to 77 students, was composed of zero percents of girl's middle school, 18.2% of girl's high school, 36.4% of boy's middle school and 45.4% of boy's high school. 10) Among the 77 students, whose shoes showed fecal coliform positive, only 6.5% of them cleaned their shoes once in a week or a month and 62.3% of them cleaned them once in a six month. 11) The fccal coliform positive rate was higher in the cloth shoes materials than the vinyl materials. 12) The concrete-bottomed building higher positive rate (40.2%) than the wood-bottomed building (7.5%). 13) Even among the student's who frequently cleaned their desk drawer, 2.3% were in the positive, and among those who were unconcerned with drawer cleaning, 48.9% were involved in the positive. 14) In the fecal coliform positive rate of bags, 38.5% of the positive rate belonged to using indoor shoes while cleaning their class bottom with water, 53.8% belonged to using outdoor shoes while cleaning their class bottom with water, 7.7% belonged to using outdoor shoes while cleaning their class with oil.

• Journal of the Korean earth science society
• /
• v.34 no.4
• /
• pp.289-302
• /
• 2013

In order to determine the provenance of the Huksan Mud Belt sediments in the southeastern Yellow Sea, the major and rare earth elements of the same sediments were analyzed. The surface sediments were sampled from top of piston-cores and box-cores taken at 51 sites within the Huksan Mud Belt. With the mean grain size of $5-6{\phi}$, the sediments of the study area are mud-dominated. The spatial distribution patterns show that silt content is high in the northern Mud Belt, whereas clay content increases as it moves toward the southern Mud Belt. Interestingly, the geochemical compositions both of major and rare earth elements have resulted in differences of sediment provenance. Among the major elements, plots of Fe/Al vs. Mg/Al ratios, $Al_2O_3$ vs. MgO ratios, and $Al_2O_3$ vs. $K_2O$ reveal that the Huksan Mud Belt sediments are dominated by the Korean river-derived sediments. However, the characteristics of rare earth elements infer sediments originating from the Chinese rivers. This discrepancy between the above provenances is attributed to the different contributory factors in the content of chemical elements. Considering strong correlation between major elements with grain sizes, the contents of the major elements are thought to be influenced by the grain size. However, there is a weak correlation between rare earth elements and grain sizes. The behaviour of rare earth elements may be controlled by heavy minerals, rather than grain sizes. Further study requires to solve the discrepancy arose from the difference in applied chemical tracers.

• Journal of the Korean Institute of Gas
• /
• v.11 no.1 s.34
• /
• pp.29-33
• /
• 2007

This study investigates the use of $TiO_{2},\;Pd,\;Pt$, and In which greatly improves a sensitivity to trimethylamine gas. The metal-$SnO_{2}$ thick films were prepared by screen-printing method onto $Al_{2}O_{3}$ substrates with platinum electrode. The sensing characteristics were investigated by measuring the electrical resistance of each sensor in a test box as a function of detecting gas concentration. This was then used to detect trimethylamine, dimethylamine, and ammonia vapours within the concentration range of 100-1000ppm. The gas sensing properties of metal-$SnO_{2}$ mixed thick films depended on the content and variety of metal. It was found that sensitivity and selectivity of the films dopped with 1 wt% Pd and 10 wt% $TiO_{2}$ for trimethylamin gas showed the best result at $250^{\circ}C$.

• Current Research on Agriculture and Life Sciences
• /
• v.7
• /
• pp.99-107
• /
• 1989

The study was conducted to obtain some basic information to establish the system of performance-tests and selection of honeybee queens(Apis mellifera) under Korean circumstances, Colony performances were tested with thirty colonies of Apis mellifera at two apiaries in Taegu, Korea from September, 1988 to August 1989. The results of performance-testing on the colonies are summarized as follows : The colony weight measured before wintering was averaged $23.6{\pm}1.90kg$ and the colony weight was decreased by $2.9{\pm}0.82kg$ in average during winter season. Thirteen colonies were entered in two story hive from thirty single box colonies from April 17 to May 5, 1989 with increase of bee population and, consequently, the ability of enter-supers of the colonies apperared to be low. The ability of collecting pollen was measured to be $14.8{\pm}2.15gr$ per colony during 24 hours in April, and the number of swarm cells was counted $12.5{\pm}3.43$ cells per colony in aveage. Tendency to use propolis appeared to be moderate, and the number of returning foragers for a minute per colony was counted $108.7{\pm}18.31$ bees in average. Brood area was measured $2,464{\pm}628,67cm^2$ per colony in the post nectar flow season of acasia, and 30.8 percent of the colonies appeared to be infected with chalkbrood disease, The amount of honey production was $14.9{\pm}8.49kg$ per colony, which was harvested two times during the main nectar flow season of acasia.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.11
• /
• pp.259-272
• /
• 2019

Steel-concrete single-leaf blast-resistant doors are protective structures consisting of a steel box and reinforced concrete slab. By the domestic blast-resistant doors, the structure is not designed efficiently because few studies have examined the effects of variables, such as the blast pressure, rebar ratio, and steel plate thickness on the structural behavior. In this study, the structural behavior of the doors was analyzed using the FE method, and the support rotation and ductility ratio used to classify the structural performance were reviewed. The results showed that the deflection changes more significantly when the plate thickness increases than when the rebar spacing is a variable. This is because the strain energy absorbed by the door is reduced considerably when the plate thickness increases, and as a result, the maximum deflection becomes smaller. According to a comparison of the calculated values of the support rotation and the ductility ratio, the structural performance of the doors could be classified based on the support rotation of one degree and ductility ratio of three. On the other hand, more explosion tests and analytical studies will be needed to classify the damage level.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.11
• /
• pp.520-526
• /
• 2019

I-type girders are widely applied as very economical sections in plate girder bridges. There has been research on developing composite laminated panels, curved plates reinforced with closed-end ribs, and new forms of ribs and compression flanges for steel box girders. However, there is a limitation in analyzing the exact cause of local buckling caused by an I-type girder's webs. Therefore, an I-type girder's web was modeled using the finite element analysis program LUSAS 17.0 before and after reinforcement. We checked for the minimum thickness criteria presented in the Korea highway bridge design code, and the cause of buckling after performing a linear elastic buckling analysis of dead and live loads was analyzed. Before reinforcement, an eigenvalue (λ₁) at the 1st mode was 0.7025, the critical buckling load was smaller than the applied load, and there is a buckling. After reinforcement, when applying vertical and horizontal stiffeners to the web part of the girder at support, a Nodal line was formed, the eigenvalue was 1.5272, and buckling stability was secured. To improve buckling trace of the girder at the support, an additional plate was applied to the web at the support to ensure visual and structural safety, but buckling occurs at center of web. The eigenvalue (λ₁) was 3.5299, and this method is efficient for reinforcing the web of the support.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.21 no.11
• /
• pp.683-692
• /
• 2020

A joint displacement resistance evaluation method for selecting waterproofing materials in railway bridge decks is proposed. The displacement range for an evaluation is determined by finite element method (FEM) analysis of a load case based on an existing high-speed PSC Girder Box railroad bridge structure. The FEM analysis results were used to calculate the minimum joint displacement range to be applied during testing (approximately 1.5 mm). For the evaluation, four commonly used waterproofing membrane types, cementitious slurry coating (CSC), polyurethane coating system (PCS), self-adhesive asphalt sheet (SAS), and composite asphalt sheet (CAS), were tested, with five specimens of each membrane type. The joint displacement width range conditions, including the minimum displacement range obtained from FEM analysis, were set to be the incrementing interval, from 1.5, 3.0, 4.5, and 6.0 mm. The proposal for the evaluation criteria and the specimen test results demonstrated how the evaluation method is important for the sustainability of high-speed railway bridges.

• Journal of the Korean Society of Safety
• /
• v.31 no.5
• /
• pp.22-27
• /
• 2016

The Electrostatic Charge Prevention Technology is a core factor that highly influences the yield of Ultra High Resolution Flat Panel Display and high-integrated semiconductor manufacturing processes. The corona or x-ray ionizations are commonly used in order to eliminate static charges during manufacturing processes. To develop such a revolutionary x-ray ionizer that is free of x-ray radiation and has function to control the volume of ion formation simultaneously is a goal of this research and it absolutely overcomes the current risks of x-ray ionization. Under the International Commission on Radiological Protection, it must have a leakage radiation level that should be lower than a recommended level that is $1{\mu}Sv/hour$. In this research, the new generation of x-ray ionizer can easily control both the volume of ion formation and the leakage radiation level at the same time. In the research, the test constraints were set and the descriptions are as below; First, In order not to leak x-ray radiation while testing, the shielding box was fully installed around the test equipment area. Second, Implement the metallic Ring Electrode along a tube window and applied zero to ${\pm}8kV$ with respect to manage the positive and negative ions formation. Lastly, the ion duty ratio was able to be controlled in different test set-ups along with a free x-ray leakage through the metallic Ring Electrode. In the result of experiment, the maximum x-ray radiation leakage was $0.2{\mu}Sv/h$. These outcome is lower than the ICRP 103 recommended value, which is $1{\mu}Sv/h$. When applying voltage to the metallic ring electrode, the positive decay time was 2.18s at the distance of 300 mm and its slope was 0.272. In addition, the negative decay time was 2.1s at the distance of 300 mm and its slope was 0.262. At the distance of 200 mm, the positive decay time was 2.29s and its slope was 0.286. The negative decay time was 2.35s and its slope was 0.293. At the distance of 100 mm, the positive decay time was 2.71s and its slope was 0.338. The negative decay time was 3.07s and its slope was 0.383. According to these research, the observation was shown that these new concept of ionizer is able to minimize the leakage radiation level and to control the positive and negative ion duty ratio while ionization.

• Journal of KIISE:Software and Applications
• /
• v.31 no.8
• /
• pp.1027-1042
• /
• 2004

A Software Component is a module that is reused among a lot of projects, systems, and companies rather than a single application. Components can be reused in various systems if they provide not only the common functionalities required in many applications but also the diverse aspects to be customized for being suitable for customers' demands. From the development phase, components should be designed and developed considering the variable aspects they have for convenient customization. Easily customized components can be frequently reused in lots of applications. In the literature, there are some modeling and customizing techniques. But they suggested only conceptual or basic methods based on Object-Oriented. And the practical instructions for reusing component were not provided sufficiently. Moreover, there are few techniques that consider the proper variability types components have. Thus, those techniques are not appropriate for applying to black box component completely developed and released. In this paper, we classify variabilities that components have in functional aspect into two categories. The one is logic variability, and the other is workflow variability. For each classified variability, we propose the three kind of modeling techniques, which are selection, plug in and externalization. Also detailed instructions for practical design and application are provided.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.12 no.8
• /
• pp.3729-3744
• /
• 2011

As the size of structures become larger by civil and architectural structures becoming large, deeply underground, and high-rise, the conditions of underground foundation vary according to the location that the lack of bearing capacity locally because of ununiform of foundation in some parts is frequent. Generally, when the foundation is not homogeneous, the acquisition of safety through applying the most conservative foundation method possible becomes the focus to secure the stability of the superstructures. It is considered as because of inability to verify the application and stability and application of construction of different foundations through an outlined review because of lack of study in case of different foundation of mixed use of direct foundation and pile foundation. Therefore, through measurement interpretation of the different foundation in which the direct foundation and pile foundation are mixed in use, the grounds in which the hypothetical bearing capacity changes dramatically was modeled to evaluate the applicability of different foundations. Also, based on the results of measurement interpretation, various foundations are created by using plaster, Joomunjin standard soil, and rubble to conduct an indoor model test to compare and analyze the movement of pile foundation and different foundations. Based on such research results, the stability and applicability of the different foundations which is more efficient and economical than the existing foundations in case of grounds in which the bearing capacity changes dramatically by comparing and analyzing the different foundations (direct foundation + pile foundation) with the conservative pile foundation and mat foundation. As a result, when the different foundation is applied, the overall settlement amount increased than the conservative pile foundation. However, the difference was very minute and it has been confirmed to be no issue as a result of assessment of stability of the differential settlement of structures through critical angle displacement.