• Journal of the Korean Geosynthetics Society
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• v.16 no.2
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• pp.109-119
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• 2017

In this research, it was investigated that whether the upper sand deposited in Nakdong River Estuary Delta region has the role of horizontal drains like sand mat. The results from tests for particle size distribution and permeability of the upper sand deposit did not meet completely the criteria for the horizontal drain material. Thus, numerical analysis has been conducted additionally. Numerical analyses of consolidation of soft soils with upper layer of sand deposit are conducted in both the sand mat with a thickness of 1m and the upper sand deposit with 1, 2, 3, and 4 m of thickness and their results are compared. As the results of numerical analysis, the upper sand deposit with a thickness of 2m or more may play the role of horizontal drains similar to a sand mat. If a PVD is installed, the ability of upper sand deposit as horizontal drains is increased. Form this study, it was concluded that the upper sand deposited in Nakdong River Estuary Delta has the role of horizontal drain.

• Journal of the Korean Geotechnical Society
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• v.27 no.1
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• pp.17-24
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• 2011

The characteristics of flow and strength of CLSM depend on the combination ratio including the fly ash, pond ash, cement, water quantity and etc. However, it is very difficult to draw the mechanism about the flow, strength and the mixing ratio of each components. Therefore, the method of calculation drawing the flow about the component ratio of CLSM and compression strength value is needed for the valid practical use of CLSM. To verify the efficiency of artificial neural network, new data which were not used for establishing the model were predicted and compared with the results of laboratory tests. In this research, it was used to evaluate the learning efficiency of the artificial neural network model and the prediction ability by changing the node number of hidden layer, learning rate, momentum, target system error and hidden layer. By using the results, the optimized artificial neural network model which is suitable for a flow and compressive strength estimate of CLSM was determined.

• Journal of the Korean earth science society
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• v.30 no.2
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• pp.257-264
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• 2009

The purpose of this study was to examine the effects of the game application learning 8th graders' scientific attitude, which was utilized as a strategy to improve the teaching skills and methods in the lesson of 'the history of the earth and diastrophism'. The subjects of this study were 120 students of 8th grade at a middle school located in a metropolitan city in Korea. To start off with homogeneity of a group, this study recruited participants by the results of a diagnostic test taken early in the year and a mid-term examination taken at the end of April. As a result, a total of 4 male classes that showed similar results on the two tests were selected and divided into two groups: one in experimental and the other in control. In addition, the top 20% students and the low 20% students were chosen for comparison of their scientific attitudes based on the results of the mid-term examination. The traditional teachings were offered to the control groups while the experimental lessons with the game activities performed at the stages of application and summary in teaching were offered to the experimental groups over 10 periods. Results of the pre- and post-test on the students' scientific attitude demonstrated that there was a statistical significance between the two groups, which suggested that the experimental group showed a meaningful improvement in the scientific attitude after experimental intervention lesson activities with game applications. Also, the more meaningful improvement in the scientific attitude was found in the lower group than in the higher group. It implies that lessons with the game activities motivated the students to voluntarily participate in school science learning by enhancing their interests. Therefore, it is suggested that game application learning be a new teaching-learning material that helps to encourage learners to actively participate in middle school science learning.

• Journal of the Korean Electrochemical Society
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• v.18 no.4
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• pp.156-160
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• 2015

Experiments using a metal oxide of a non-nuclear material as a fuel are very useful to develop a new electrolytic reducer for pyroprocessing. In this study, the titanium oxides (TiO and $TiO_2$) were selected and investigated as the non-nuclear fuel for the electrolytic reduction. The immersion tests of TiO and $TiO_2$ in a molten 1.0 wt.% $Li_2O$-LiCl salt revealed that they have solubility of 156 and 2100 ppm, respectively. Then, the Ti metals were successfully produced after the separate electrolytic reduction of TiO and $TiO_2$ in a molten 1.0 wt.% $Li_2O$-LiCl salt. However, Ti was detected on the platinum anode used for the electrolytic reduction of $TiO_2$ unlike TiO due to the dissolution of $TiO_2$ into the salt.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.3
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• pp.404-410
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• 1989

Friction and wear tests were conducted with several different ceramics sliding against ceramic and metal couples with and without lubricant in a two disk type sliding machine. The purpose was to know the tribological properties of ceramics. With very different physical and chemical properties of ceramics compared to metal, the tribological properties of ceramics should be defined in detail. Among them, the wear and friction with same or different couple is very important. Also the lubrication of ceramic is one of the major area to be studied. From this research, SiC, SI$_{3}$N$_{4}$ and ZrO$_{2}$ were slid against SiC, AISI 4340 and bronze under various sliding condition. It was found that the friction and wear of ceramics are strongly dependent on the sliding condition. For unlubricated sliding against SiC, ZrO$_{2}$ shows low wear and friction coefficient over wide lange of load, but with lubricated sliding, SiC shows better performance whatever lubricants were used. Also the effect of lubricant depended upon the material properties of sliding pairs. The general tribological properties of ceramics were not correlated with chattering and noise at low load but it could be reduced or avoided effectively by using lubricants. SiC and Si$_{3}$N$_{4}$ slid against SiC have transition from mild to severe wear at high load but ZrO$_{2}$-SiC and SiC-steel have not. Wear debris formed on the contact area of SiC couples was main cause of the initiation of transition. At high speed, only ZrO$_{2}$ sliding against SiC has transition of wear by low thermal conductivity.

• Journal of the Korean Society of Safety
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• v.20 no.4 s.72
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• pp.171-179
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• 2005

It is essential to understand the role of wall lining materials when they are exposed to a fire from an ignition source. Full-scale test methods permit an assessment of the performance of a wall lining material. Fire growth models have been developed due to the costly expense associated with full-scale testing. The models require heat flux maps from the ignition burner flame as input data. Work to date was impeded by a lack of detailed spatial characterization of the heat flux maps due to the use of limited instrumentation. To increase the power of fire modeling, accurate and detailed heat flux maps from the ignition burner are essential. High level spatial resolution for surface temperature can be provided from an infrared camera. The objective of this study was to develop a heat flux mapping procedure for a room test burner flame to a wall configuration with surface temperature information taken from an infrared camera. A prototype experiment was performed using the ISO 9705 test burner to demonstrate the developed heat flux mapping procedure. The results of the experiment allow the heat flux and spatial resolutions of the method to be determined and compared to the methods currently available.

• Applied Biological Chemistry
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• v.11
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• pp.123-130
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• 1969

Five varieties of sweetpotatoes recommended in Korea were investigated with respect to the storing capacity, resin content and the possibility of developing sweetpotato chips as a new processed food item. The results are summarized as follows: 1) Two varieties, Suwon No. 147 and Chun-Mi were more resistant to chilling injury and soft-rot decay than other varieties. 2) The contents of resinous and polyphenolic substances were quite different depending upon the variety. 3) Sweetpotato chips of different color were made from different varieties and rapeseed oil was found to be the best as frying oil. 4) Best conditions to prepare sweetpotato chips with fresh color and proper texture were to dip slices of 1-2 mm thickness in 0.25% sodium bisulfite solution at $40^{\circ}C$ for 30-40 minutes and to subject to deep frying in an oil bath at $150-160^{\circ}C$ for 2.5 to 3.5 minutes. 5) Polyethylene-cellophane film as packing material of sweetpotato chips was the film in the moisture proof and film-impact tests.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.1
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• pp.698-704
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• 2020

Although various biological extracts derived from the resources from Jeju are currently being developed for cosmetic materials, few studies using Brown algae from Jeju have been conducted. This study identified materials with high antioxidant levels and examined their whitening effects to assess their feasibility as potential cosmetic resources. Brown algae from Jeju (Undaria pinnatifida (Harvey) Suringar, Laminaria japonica, Ecklonia cava, Hizikia fusiforme (Harvey) Okamura (HF), and Sargassum fulvellum (Turner) C. Agardh (SF) were processed using a supercritical fluid system at 50℃ and 400 bar, and their total phenol content, antioxidant activity, tyrosinase inhibition, and primary skin irritation were measured. Of all the samples, only SF using the supercritical fluid system (SFS) displayed concentration-dependent behavior for the total phenol content (p<0.05). Among the samples, the antioxidant activity of SFS was significantly higher (p<0.05) and the one increased at higher concentrations (p<0.05). On the other hand, tyrosinase was inhibited to a greater extent with HF than the others. The primary skin irritation tests showed that none of the samples were skin irritants. This study confirmed the feasibility of using Phaeophyceae from Jeju as potential cosmetic materials, where the samples can be selected and utilized based on the required physicochemical properties.

• 대한공업교육학회지
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• v.31 no.2
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• pp.41-63
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• 2006

The purpose of this study was to establish and apply 'term learning strategy' for learners whose basic skill, interest, and motivation for learning is lower, and to increase the learned capabilities of subjects' 'industry introduction', required for industrial technical high school students. Another purpose was to identify when the learning strategy established was applied, its affect on how well learners understood terms in a particular unit of material, and, after instruction presented in accordance with 'term learning strategy,' evaluate the ease with which subjects understood the teacher's explanation of the unit of subject, how well they understand the main concepts of the unit of subject, and to what extent the presentation interested and motivated the subjects. The researcher established 'term learning strategy' based on the principles of Garg's "Nine Steps for Events of Instruction." The study included 35 first grade participants purposely selected from 33 classes at 1155 students in K industrial technical highschool. Data was collected via tests and surveys. Results indicated that 'term learning strategy' facilitated thorough understanding of terms and concepts related to the unit of subject, as well as a better understanding of the teacher's explanation and increased interest and motivation in learning. In addition, the "term learning strategy" increased interaction among learners in the instruction setting. Finally, implications of this study and implementation recommendations for this instructional strategy were presented.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.5
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• pp.709-716
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• 2016

Recently, the operating conditions of the various mechanical structures have become more severe and the running time has become longer as the development of plant equipment increases with the introduction of high technology. Thus, the reliability of the system and its accessories is becoming a problem. Normally, synthetic natural gas (SNG) plants use 1.25Cr-0.5Mo or 2.25Cr-1Mo heat resistant steel according to the operating conditions. In this study, a lab-scale reactor was set up using 1.25Cr-0.5Mo steel, in order to carry out corrosion tests for producing synthetic natural gas. The corrosive characteristics were investigated under 1st-methanator operating conditions and fundamental data about the durability and reliability were obtained by using the experimental test. The analysis of results obtained on the durability of the reactor under emission and injection compositions showed that the hydrogen embrittlement caused by hydrogen and the oxidation corrosion caused by H2O had the most effect on the durability of 1.25Cr-0.5Mo steel in the SNG reactor. However, the hydrogen embrittlement and oxidation corrosion occurred simultaneously under emission conditions, so that the corrosion of the material increased suddenly after a long operating time. Besides, the corrosion of the 1.25Cr-0.5Mo steel under the injection composition was faster than that under the emission composition.