• Korean Journal of Ecology and Environment
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• v.34 no.4 s.96
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• pp.267-276
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• 2001

The downstream reach of the Han River adjoining Seoul in Korea was the upper boundary of an estuary where tidal effect on the flow rate could be exerted. According to the comprehensive river regulation project, the river was channelize dand impounded by two overflow dams, which provided favorable condition for algal growth in this sewage polluted eutrophic reach. In this study primary productivity of phytoplankton was measured in the down reach and the autochthonous and allochthonous organic carbon loadings were estimated. Primary production of phytoplankton measured by C-14 uptake and P-I model method ranged from 140 to $4,890\;mgC\;m^{-2}\;d^{-1}$ (median value $1,865\;mgC\;m^{-2}\;d^{-1}$) showing the level of eutrophic lakes. Phytoplankton density that varied according to water flow rate was highest in spring. Allochthonous organic carbon loading was dominated by sewage input through tributaries in most of days except flood flow period. The average proportion of autochthonous carbon generation by phytoplankton was 40.9%, which is very high proportion for a lotic habitat.

• Korean Journal of Ecology and Environment
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• v.33 no.4 s.92
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• pp.387-394
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• 2000

Water pollution characteristics were investigated in the Kyongan stream and major inlet parts of Paltang Reservoir from April to July, 2000. Water quality in the Kyongan stream was extremly deteriorated by treated wastewater discharge at near sewage wastewater treatment plant (SWTP) located in the upstream, and it is likely to influence eutrophication of the lower part of the stream. Water quality of the Kyongan stream showed a typical hypertrophic condition. Influxed concentrations with $NH_4$ and SRP into the main stream from SWTP were declined precipitously as water flowed toward the lower part of the stream, and chlorophyll- a explosively increased in the midstream. Average concentrations of $NH_4$, SRP and chlorophyll-a in the main stream were $1,343\;{\mu}g\;N/l$, $1,779\;{\mu}g\;P/l$ and $188\;{\mu}g\;l$, respectively. Particularly, phosphorus load was very high, and its influence on the algal growth stimulation was remarkable. In comparison with the water quality inflowing into Paltang Resevoir, pollution status of the Kyongan stream was more worse than that in the Pukhan River and the Namhan River. The results of this study indicate that the management of point source, SWTP effluent, is urgent to mitigate eutrophication of Paltang Reservoir, and requires further necessary controls of inorganic phosphorus loading.

• Journal of Korean Society of Steel Construction
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• v.27 no.2
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• pp.155-167
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• 2015

If of application of the deep deckting floor in long span more than 6m, the deflection caused by the construction load occurred high. Because the constructing-works and safety by this deflection, take actually supports to laborers working on the deck. However, installed supports are having difficultly such as the restricted passage, deficiency of working space, and lowering of efficiency. And toward-opening deck is seen as local buckling of web plate, flexural-torsional buckling, and gradually opening of corrugated decking. In this study, we will suggest a deep decking floor system that reinforced with both ends cap plates for toward-opneing decking change from opening to closing. The constructing deflection of a deep decking more than 6m must be satified 30mm and L/180 as proposed. Full-scale field tests loading by sand conducted a deep decking reinforced with and without cap plate. In conclusion, the specimen reinforced with cap plates have shown that to ensure the negative moment $wl^2/18$. And constructing-deflection of deep decking shown that to satisfy the evaluation value (L/180 or 30mm).

• Journal of the Korea Concrete Institute
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• v.15 no.2
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• pp.234-245
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• 2003

Most of the concrete bridge structures are exposed to damage due to the excessive traffic loading and the aging of the structure. The damage of concrete causes the further deterioration of the function in the concrete structure due to corrosion of the reinforced bars and decohesion between the concrete and the reinforced bar. The quick rehabilitation of the damaged concrete structures has become of great importance in the concrete structural system in order to avoid the further deterioration of the structures. Recently fiber sheets are used for strengthening the damaged concrete structures due to its many advantages such as its durability, non-corrosive nature, low weight, ease of application, cost saving, control of crack propagation, strength to thickness ratio, high tensile strength, serviceability and aesthetic. However, the lack of analytical procedures for assessing the nominal moment capacity by the fiber sheet reinforcement leads to difficulties in the effective process of decisions of the factors in the strengthening procedure. In this work, flexural strengthening effects by fiber sheets bonded on bottom face of the member are studied for the reinforced concrete T beam. In addition, auxiliary flexural strengthening effects by U-type fiber sheets bonded on bottom and side faces of the member to prevent delamination of the bottom fiber sheet are theoretically investigated. The analytical solutions are compared with experimental results of several references to verify the proposed approach. It is shown that the good agreements between the predicted results and experimental data are obtained.

• Journal of Technologic Dentistry
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• v.33 no.4
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• pp.299-306
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• 2011

Purpose: This study aimed to investigate the shear bond strength by manufacturing the veneering porcelain on the IPS e.max $ZirCAD^{(R)}$ zirconia core, using the layering technique and heat-pressing technique, and to evaluate the clinical stability by comparing to the conventional metal ceramic system. Methods: The Schmitz-Schulmeyer test method was used to evaluate the core-veneer shear bond strength of zirconia core ceramic(IPS e.max $ZirCAD^{(R)}$) and their manufacture recommended two veneering ceramic systems(IPS e.max $ceram^{(R)}$, IPS e. max $ZirPress^{(R)}$). A metal ceramic system(Bellabond $plus^{(R)}$, VITA $VM13^{(R)}$) was used as a control group for the two all ceramic system test groups. The maximum loading and shear bond strength was measured. The average shear strength(MPa) was analyzed with the one-way ANOVA and the Tukey's test(${\alpha}$=.05). The fracture specimens were examined using Microscope to determine the failure pattern. Results: The mean shear bond strengths(SD) in MPa were MBSB control 43.62(2.13); ZBSB 18.65(1.76); ZPSB 18.89(1.54). The shear strengths of the zirconia cores were not significantly different(P>.05). Microscope examination showed that zirconia specimens presented mixed failure, and base metal alloy specimens showed adhesive failure. Conclusion: There was no siginificant different between the layering technique and the heat pressing technique in the veneering methods on the zirconia cores. None of the zirconia core and veneering ceramics could attain the high bond strength values of the metal ceramic combination.

• Journal of the Korean Geotechnical Society
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• v.19 no.4
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• pp.235-246
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• 2003

Since the study of Lee et al.(1994) there have been some case studies on the set-up effect of driven piles in Korea country. However, comprehensive examination on the analyses of the set-up effect with various testing data has not been carried out. In particular, the analysis of the influence of soil type and pile shape on the set-up effect has not been reported. It is necessary to analyse the test results of production piles in order to apply the set-up effect of driven piles for the field engineering. In this study some test piling and analyses were performed to give basic information to the piling design as well as the research on the set-up effect in sandy soils. The analyses on the set-up effect were performed with the monitoring data obtained from the high-strain dynamic loading tests. It was shown that the set-up effect of driven piles was not only affected by soil type but also by soil formation history It turned out that the set-up effect in sandy soils was considerable one that should not be ignored in the field, and that the bearing capacity increase of pile is mainly caused by the increase of shaft resistance. It was shown that the set-up effect of closed pile was larger than that of opened pile in clayey soils, while the set-up effect of opened pile was larger than that of closed pile in sandy soils.

• KSBB Journal
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• v.11 no.5
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• pp.577-585
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• 1996

Effects of various factors on the phenol degradation by activated sludge immobilized with the photo-crosslinked resin were investigated. The optimum pH on the degradation of phenol in both free and immobilized activated sludge was 7. When the pH of the reaction was varied from 5 to 10, the relative activity of the phenol degradation by the immobilized activated sludge was higher than that by the free activated sludge. A higher rate of phenol degradation was observed when a bead size was smaller. The phenol degradation in the free activated sludge was inhibited at the 3000 mg/L of phenol, while that in the immobilized activated sludge was maintained at the same concentration for 28 hrs without an inhibition. The degradation rates of phenol were not directly proportional to the increasing amount of immobilized beads dosage, but the phenol degradation was made in a rather short time than that for a free sludge system. The relative activities of the immobilized activated sludge after 7 runs of repeated reactions increased about 8 times as that of the first reaction. The activities for the phenol degradation remained stable for at least 80 days when the immobilized activated sludge was stored at an aerobic condition in the wastewater containing phenol. The loading rate as high as 5.59 kg-pheno1/㎥.d could have been achieved during the continuous treatment of phenol by the immobilized activated sludge.

• 대한공업교육학회지
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• v.34 no.1
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• pp.252-273
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• 2009

Due to the importance of biotechnological literacy, the educational community in fields such as technology education, science education, and agricultural education has acknowledged the importance of biotechnology instruction for secondary school. Although recognized as a content organizer in the field of technology education, the actual teaching of biotechnology has not been broadly implemented in technology education classes. In the perspective of expectancy-value theory, technology teachers' motivation is the key factor for affecting the biotechnology instruction. This study investigates Korean technology teachers' motivational beliefs toward biotechnology and its instruction and their perceived ability and value toward biotechnology learning contents. To measure their motivational beliefs and attitudes, a composite on-line survey (fifteen motivational beliefs items, eight biotechnology content items, and related demographic items) was developed. Based on 114 Korean technology teachers' responses the researcher performed a descriptive analysis, independent t-test, and factor analyses (exploratory and confirmatory factor analysis using M-plus 5.0 and SPSS 16.0). Korean technology teachers' abilities toward eight biotechnology contents indicated lowscores while their values were relatively high. Through the independent sample t-test by two demographic variables (gender and professional development), this study found several significant differences in the perceived value. As a preliminary finding of exploratory factor analysis, fifteen items was separated into two motivational constructs of expectancy (6 items) and value (8 items). One item (item #6) was eliminated due to the cross loading. The final findings of this study may have significant implications for professional development regarding biotechnology and its instruction (both in-service and pre-service training) of technology teachers. Also, the confirmatory facctor analysis supported the preliminary finding. Finally, this study recommends that a validity test for other population, investigation for motivational sub-constructs, and in-depth investigation toward biotechnology instruction.

• Journal of Korean Society of Forest Science
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• v.101 no.4
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• pp.619-625
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• 2012

This study was conducted to investigate the variation of fruit, seed and germination characteristics among populations of Serrateleaf Pearlbush (Exochorda serratifolia S. Moore) distributed in Korea. Fruits collected from 96 trees in five natural populations and their five fruit, seven seed and three germination characteristics were analyzed. In 14 characteristics except for mean germination time, there were significant differences among populations and among individuals within population. Generally, fruit and seed characteristics showed higher values among population in total variance component. Coefficients of variations in weight of fruit (27.0%), length/thickness of seed (28.1%) and germination rate (52.5%) were relatively high compared to other traits. In seed germination behaviors, germination percentage, mean germination time and germination rate showed 62.9%, 64.0 days and 0.40 ea./day, respectively. As a result of simple correlation analysis, mean germination time showed a significant positive correlation with seed thickness, germination rate showed a significant positive correlation with height of parent tree and latitude, respectively. Also, latitude showed a positive correlation with fruit weight. The populations close geographically did not show the tendency of clustering into the same group. The results of principal component analysis showed that the first for principal components (PC's) explained 63.0% of the total variation. Primary 3 principal components appeared to be major variables because of the loading contribution of 97.0%.

• The korean journal of orthodontics
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• v.30 no.6 s.83
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• pp.677-685
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• 2000

Anchorage plays an important role in orthodontic treatment. Because of limited anchorage Potential and acceptance problems of intra- or extraoral anchorage aids, endosseous implants have been suggested and used. However, clinicians have hesitated to use endosseous implants as orthodontic anchorage because of limited implantation space, high cost, and long waiting period for osseointegration. Titanium miniscrews and microscrews were introduced as orthodontic anchorage due to their many advantages such as ease of insertion and removal, low cost, immediate loading, and their ability to be placed in any area of the alveolar bone. In this study, a skeletal Class II Patient was treated with sliding mechanics using M.I.A.(micro-implant anchorage). The maxillary micro-implants provide anchorage for retraction of the upper anterior teeth. The mandibular micro-implants induced uprighting and intrusion of the lower molars. The upward and forward movement of the chin followed. This resulted in an increase of the SNB angle, and a decrease of the ANB angle. The micro-implants remained firm and stable throughout treatment. This new approach to the treatment of skeletal Class II malocclusion has the following characteristics . Independent of Patient cooperation. . Shorter treatment time due to the simultaneous retraction of the six anterior teeth . Early change of facial Profile motivating greater cooperation from patients These results indicate that the M.I.A. can be used as anchorage for orthodontic treatment. The use of M.I.A. with sliding mechanics in the treatment of skeletal Class II malocclusion increases the treatment simplicity and efficiency.