• Journal of the Korea Institute of Building Construction
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• v.11 no.2
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• pp.162-170
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• 2011

As the result of implementing a treated material test and durability test after quickly drying S.P.F. species, a type of softwood structural material, within a short period time, soaking it in liquid phosphate flame proof agent for an hour, microwave heating it, and compressing it from 3.8cm to 1cm, when setting the appropriate heating time of microwave heating at 7 minutes at 5kW, it is observed that it satisfies the target water content (4~5%). It is shown that in a water content measurement of the wood that is compressed after being softened by soaking in the flame proof agent, drying and heating at 3kW for 9 minutes, all specimens satisfied 12~14%, the appropriate water content for exterior wood. Also, it is shown that in terms of the flame performance obtained through a flame resistance treatment of the compressed wood and a treated material test, the specimen soaked in flame proof agent for 30 minutes was the most excellent, and that the performance test result of the compressed wood in all areas, such as nail withdrawal resistance, compression, bending strength, and shearing strength, were all improved in their mechanical features to twice to three times better performances.

• Journal of the Korean Geotechnical Society
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• v.17 no.6
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• pp.235-244
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• 2001

Liquefaction may be caused by sudden decrease in the soil strength under undrained conditions. This loss of soil strength is related to the development of excess pore pressures. During this study, fines content affects the maximum and minimum void ratios are investigated. The results of static and cyclic triaxial test on silty saturated sands are presented. These tests are performed to evaluate liquefaction strength and static and cyclic behavior characteristics. The samples are obtained from Saemangeum and drying on air. The main results are summarized as follows : 1) The maximum and minimum void ratio lines follow similar trends. 2) Maximum and minimum void ratios are established at 20~30% fines content. 3) As confining pressures and overconsolidation ratio are increased, the resistance to liquefaction are increased. 4) Instability friction angles are increased with increasing initial relative density. 5) The resistance to liquefaction are decreased with increasing effective stress ratio.

• Proceedings of the KIEE Conference
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• 2006.07a
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• pp.452-453
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• 2006

저압 개폐기는 에어컨, 냉동기, 쇼케이스, 산업용 청소기, 전기 온수기, 건조기, 공조기, 펌프, 콤프레셔 등의 모터제어 및 히터와 조명기기의 개폐 등에 광범위하게 이용되는 개폐장치이다. 저압 전자개폐기는 수 천회에서 수백만회까지 빈번한 개폐사용조건으로 인해 시험규격에서는 개폐시험을 통해 수명을 검증하도록 되어 있다. 이 개폐시험 회로는 규정된 전압, 전류, 역률 조건을 맞추기 위해 저항과 리액터를 직렬 연결하여 구성한다. 또한 모터와 같은 리액터 부하를 개폐하는 개폐기의 경우는 전류차단 순간 과도회복전압의 피크비와 주파수를 규정하여 적용하고 있다. IEC60947-1에서는 과도회복전압의 피크비와 주파수에 대한 규정값을 제시하고 있으며 제시된 값을 제어하기 위한 회로를 제시하고 있다. 과도회복전압의 피크비와 주파수는 개폐기 접점의 절연성능과 밀접한 관계가 있으며 수명에 치명적인 영향을 미친다. 본 연구에서는 LS산전(주) 부하개폐시험 회로의 과도회복전압 조건과 영향을 설명하고 제어하기 위한 저항과 커패시터를 적용하는 방법을 제안하고자 한다.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.05a
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• pp.127-128
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• 2017

Tests are conducted according to the ISO TS 16774, Part 3 standard for quality management of leakage repair materials used in cracks in underground concrete structures. These test methods are performed indirectly using a nonwoven fabric on a chalet containing leak repair materials. However, it is considered that it is appropriate to verify the resistance of the repair material, which is required to be applied directly to the cracks in the actual field and to exhibit the resistance of the flow velocity. In this study, mass change was measured by using nonwoven fabric and nonwoven fabric. As a result, both methods showed an increase in mass, which indicated that the maintenance material itself contained a large amount of water, and that the mass change occurred depending on the drying state. Also, depending on the use of nonwoven fabric, the error due to the indirect test could not be ruled out. Therefore, further verification is needed, and it is considered that the test for change of mass reduction measurement is necessary according to the drying time of other types of the same series.

• Journal of the Korean GEO-environmental Society
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• v.18 no.10
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• pp.23-34
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• 2017

As the electrical property of fully saturated soils is dependent on the pore water, it has been commonly used for the detection of the contamination into the ground. The objective of this study is to investigate the electrical characteristics according to the salinity and the lead concentration in fully saturated soils. Fresh water and saline water with the salinity of 1%, 2% and 3%, which are mixed with 6 different lead solutions with the range of 0~10 mg/L, are prepared in the cylindrical cell incorporated with sensors for measuring electrical resistance and time domain reflectometry signal. Then, the dried sands are water-pluviated into the cell. The electrical resistance and the time domain reflectometry signal are used to estimate the electrical conductivity. Test results show that electrical conductivity determined from electrical resistance at the frequency of 1 kHz continuously increases with an increase in the lead concentration, thus it may be used for the estimation of the contaminant level. In addition, the electrical conductivity estimated by the time domain reflectometry changes even at very low concentration of lead, the variation rate decreases as the lead concentration increases. Thus, the time domain reflectometry can be used for the investigation of the heavy metal leakage. This study demonstrates that complementary characteristics of electrical resistance and time domain reflectometry may be used for the detection of the leakage and contamination of heavy metal in coastal and marine environments.

• Journal of the Korean Geosynthetics Society
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• v.14 no.2
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• pp.71-79
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• 2015

This paper describes vegetation based soil-media hydroseeding measures that have been previously applied as slope revegetation methods show problems such as insufficient binding force, drying, and insufficient organic matter. In particular, in the case of slope faces in regions where scattering is severe, a vicious circle exists in which remarkably low vegetation cover rates and increases in withering rates over time lead to further decreases in vegetation cover rates, which lead to further increases in erosion and scattering. Therefore, in the present study, environment friendly soil stabilizers were applied for resistance against erosion or scattering and engineering evaluations such as long-term immersion tests and flow resistance tests were conducted to determine appropriate mixing ratios. According to the results of long-term immersion tests utilizing environment friendly soil stabilizers and existing greening soil based materials, 100% collapse occurred at 30 hours and 40 days in the case of soil stabilizer mixing ratios of 0% and 2%, respectively. While the original form of the samples remained intact until the experiment was completed in the case of mixing ratios exceeding 4% indicating that 2% or higher soil stabilizer mixing ratios could affect the maintenance of forms even under extreme conditions. In addition, artificial rainfall tests were conducted on 40, 45, and 55 degree slope faces to evaluate the structural stability of vegetation based materials. Flow resistance tests were conducted on soil stabilizer mixing ratios of 0, 4, 8% to evaluate erosion resistance capability. Based on the results of the tests, environment friendly soil stabilizers applied for prevention of scattering or resistance against erosion by rainwater are considered to provide large effects to reduce losses and loss rates showed a tendency of decreasing rapidly when soil stabilizers were mixed.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.633-636
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• 2008

In order to efficient use of land and development of human, a lot of research on the utilization of underground space is being progress. For the smooth flow of traffic, in the case of mountainous terrain like our country, construction of the tunnel is rapidly increasing. The NATM method is used mainly in the domestic. And also, a lot of research for the NATM is underway, but aspects of the material are lacking. In this study, therefore, it is to evaluate the properties of durability according to mixing ratio and a kind of mineral admixture for the development of shotcrete performance by using the MATM.

• Magazine of the Korea Concrete Institute
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• v.9 no.1
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• pp.143-151
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• 1997

Chemical resistance of the cement mortar containing the Thermally Activated Diaomite(TAD) and H.M.(Heavy Metals) has been studied. The H.M.. extracted from EAF(Electrica1 Arc Furnace) Dust. were saturated with diatomite. The diatomite was then thermally activated at $750{\circ}C$ for 30minutes and powdeled. The powder was mixed with a portland cement on a weight basis from 0%. 2.5%. 5.0%. 10%. 20%. The optimum mixture. after those mixtures were subjected to compressive strength(7 and 28days) and leaching bchaviour of H.M.. was tested for its experiment on Wet/Dry cycles and chemical resistance(e.q. imrncrsion in 5%(Conc.) of H2S04, CaC12 and hlgSO4. It was shown that the cement, mortar containing 10% of' P.D. gave a rise to the remarkable increase in compressive strength. The compressive strength was generally decrease beyond the addition of 10% of P.D. The maximum $496kgf/cm^2$ of 28days compressive strength was acheiveti when 10% of P.D. was added to the cement mortar.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.29 no.1
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• pp.67-71
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• 1984

These experiments were conducted at field and green house in order to screen the resistant sesame varieties to Phytopthora nicotianae var. parasitica. and to ascertain the infection conditions of Corynespora cassiicola at different temperatures, soil moistures and leaf stages. Most of varieties studied in this experiment were very susceptible to the Phytopthora blight. Orotall, Suweon 7, Suweon 27 and Jochiweon were resistant to the disease. PI280795 and IS103 showed a tendency to be morderately resistant. The infected areas by Corynespora leaf blight were 15% in Kwangeui and 25% in Kimpo variety at high temperature condition of 3$0^{\circ}C$, respectively. The infection areas were 50% in Kwangeui and 70% in Kimpo variety at low temperature condition of 17$^{\circ}C$. These results indicate that the development of the leaf blight was highly increased at low temperature. The infection areas by the Corynespora were 55% in Kwangeui and 80% in Kimpo at wet soil moisture condition, and 10% in Kwageui and 15% in Kimpo at dry condition, respectively. The infection of the leaf blight was highly increased at 6 leaf stage and flowering date compared to at 10 and 20 leaf stages. The infection ratios were 20% at 6 leaf stage and 52.5% at flowering date, respectively.

• Horticultural Science & Technology
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• v.32 no.5
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• pp.684-693
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• 2014

Abiotic stress conditions such as cold, drought, and salinity trigger physiological and morphological changes and yield loss in plants. Hence, plants adapt to adverse environments by developing tolerance through complex regulation of genes related to various metabolic processes. This study was conducted to construct a coexpression network for multidirectional analysis of salt-stress response genes in Brassica rapa (Chinese cabbage). To construct the coexpression network, we collected KBGP-24K microarray data from the B. rapa EST and microarray database (BrEMD) and performed time-based expression analyses of B. rapa plants. The constructed coexpression network model showed 1,853 nodes, 5,740 edges, and 142 connected components (correlation coefficient > 0.85). On the basis of the significantly expressed genes in the network, we concluded that the development of salt tolerance is closely related to the activation of $Na^+$ transport by reactive oxygen species signaling and the accumulation of proline in Chinese cabbage.