• Korean Journal of Environment and Ecology
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• v.22 no.1
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• pp.43-58
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• 2008

For this study, which was conducted in the summer from $2004\sim2007$, 10 small and medium sized streams in Korea were selected(Munsan and Gokreung Stream in the Han River watershed, Mi, Ssanggye and Nam Stream in the Nakdong River watershed, Gapeong and Jojong Stream in the Bukhan River watershed, Cheongmi, Yanghwa and Bokha Stream in the Namhan River watershed), and plant surveys were performed using the belt transect method on the most natural 1km sections of each stream in order to clarify the natural environment condition of the plants in each stream. In the results of the plant survey, the total number of plant species recorded was 296. After selecting 121 species of those surveyed plant in order of frequency, an RDA(Redundancy Analysis) and a Pearson Correlation Analysis were performed to determine the correlation between the selected plant species and environmental factors( such as distance from channel, size of bed material, number of bars, altitude, bed slope, width of channel, and measured data of water quality) of the study sites. There was no significant correlation between the 121 plant species and altitude, bed slope, and number of bars at the research sites, but the correlation of plant species with size of bed material, width of channel, electrical conductivity, and phosphate$(PO_4-P)$ concentration was from very high to moderate. Also, the spectrum of these plant species reflects the actual environmental conditions so the method used in the study seems to be correct, but owing to the range of diversity, the results of the study seem to be difficult to extend to other streams. Nevertheless, it is expected that this data can be used as a basic material for researching plants by stream characteristics or in selecting plant species for streams.

• Journal of Conservation Science
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• v.27 no.1
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• pp.1-11
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• 2011

For the silver artifacts in the Koryo Dynasty excavated from Neungnae-ri Ganghwa island, the metallographic section analysis and hardness and chemical analysis were conducted. After making samples in the similar ratio of the composition concentration, the changes of the microstructure were checked according to the working method and temperature. The results show that those silver artifacts are Au-Cu alloys with 2 to 6 % of Cu. From the results it is judged that Cu was artificially alloyed with them to keep the proper hardness and identified that they were gilded by the amalgamation process seeing that mercury was included at the guilt layer. Also the porous texture on the surface of them could be formed at over $400^{\circ}C$, therefore, it is assumed the hot working or heat treatment at over $400^{\circ}C$ were performed. In silver artifacts made by the relief and repousse, they have the similar composition analysis to other 7 artifacts but the hardness is lower than pure silver. Consequently from differences in the hardness, it can be inferred that the low hardness of silver artifacts is concerned with manufacturing techniques.

• The Journal of Engineering Geology
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• v.27 no.2
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• pp.165-172
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• 2017

This research aims to define influence factors to perform an optimized section design and evaluate tunnel collapse risk during construction using Delphi technique. A total of five upper classification systems were constructed through literature review, pervious research analysis, and brainstorming of expert group for establishing influence factors. The $1^{st}$, $2^{nd}$, and $3^{rd}$ Delphi survey process was proceeded by panel group which is consisted 21 experts to prevent errors and bias in the expert judgement process. In Delphi $1^{st}$ survey, a total of 22 influence factors candidates were derived through open-ended questionnaire. In Delphi $2^{nd}$ survey, questionnaire was proceeded based on 7-point Likert scale method. In order to verify the validity, CVR (Content Validity Ration) analysis was performed to exclude inappropriate candidates. In the $3^{rd}$ survey, verification of influence factors was proceeded once more with the result of $2^{nd}$ survey, and lastly, a total of 14 influence factors was derived by CVR and COV (Content Validity Ration) analysis for response of experts.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.1
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• pp.35-42
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• 2020

Torsional behavior due to the plane irregularities of the piloti building can cause excessive story drift in the torsionally outermost column, which can lead to shear failure of the column. As a seismic retrofit method that can control the torsional behavior of the piloti building, the expansion of RC wall, steel frame or steel brace may be used, but such methods may hinder the openness of the piloti floor. Therefore, in this study, linear dynamic analysis and nonlinear static analysis for piloti buildings retrofitted by knee brace were performed, and seismic performance evaluation and torsion control effect of knee brace were analyzed. The results showed that the shear force of the column increased when the piloti building retrofitted by knee brace, but it was effective in controlling the torsional deformation. In case of retrofit between knee brace and column by 30°, the shear force of the column increased less than that of 60°, and the lateral displacement of column was decreased in the order of □, ◯ and Ｈ in cross-section.

• Journal of Korean Tunnelling and Underground Space Association
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• v.11 no.1
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• pp.11-22
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• 2009

Tunnel excavation with several sections and appropriate auxiliary measures such as face bolt and pre-grouting are widely used in case of weak and less rigid ground for the stability of a tunnel face during excavation. This papers first described the evaluation methods proposed in technical literature to maintain the tunnel face stable, and then studied by FEM analysis whether face reinforcement is need in what degree of ground deformation and strength features for the stability of a tunnel face when excavating by full excavation with sub-bench. Lastly, a three dimensional FEM analysis was performed to study how the tunnel face itself and the ground around the tunnel behave depending on different bolt layouts, length of bolts, number of bolts. There were relative differences in comparison of results on the stability of a tunnel face by a theoretical evaluation methods and FEM analysis, but the same in reinforced effect of face. It was found that the stability of a tunnel face can be obtained with face bolt installed longer than 1.0D (tunnel width), bolt density of about 1 bolt per every $1.5\;m^2$ (layout of grid type), and reinforcement area of $120^{\circ}$ arch area of upper section.

• Journal of the Korean GEO-environmental Society
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• v.24 no.8
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• pp.5-11
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• 2023

Due to frequent occurrences of concentrated heavy rainfall caused by abnormal climate conditions in recent years, collapses of steep slopes have been occurring frequently due to surface erosion and increased pore water pressure. Various methods are being applied to prevent slope collapses, such as increasing the resistance to movement and reducing pore water pressure. Research on these methods has been consistently conducted as they provide an efficient response to slope collapses by satisfying both the conditions of resistance to movement and pore water pressure simultaneously. Therefore, in this study, we propose an upward slope reinforcement method by burying drainage materials with an upward slope inclination, instead of the conventional horizontal application. This approach aims to satisfy both slope reinforcement and drainage functions effectively, offering a comprehensive solution for slope stabilization. Furthermore, to determine the optimal burial angle that exhibits the most effective reinforcement and drainage effects of the proposed method, we investigated the reinforcement and drainage effects under conditions where the horizontal drainage materials were set at angles ranging from 0° to 60° in increments of 10° on a representative cross-section. Additionally, indoor model experiments were conducted under the conditions of 40°, which showed the most outstanding drainage effect, and 20°, which exhibited the highest safety factor, to validate the numerical analysis results. The results showed that the burial angle of 40° exhibits a relatively higher drainage effect as with the numerical analysis results, while the angle of 20° results in inadequate drainage and observed slope collapse.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2020.08a
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• pp.100-100
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• 2020

Wheat is mainly composed of carbohydrate but it contains a moderate amount of protein, which gives a very useful characteristics to flour food such as the unique elasticity and stickiness of the dough. We developed a calibration equation for analyzing crude protein content using Near Infrared Spectroscopy to quick analyze the crude protein content of wheat germplasm stored in the National Agrobiodiversity Center, RDA, Korea. The 1,798 wheat germplasms were used to draw up the calibration formula. The crude protein's interval distribution of 1,798 wheat germplasms used for the calibration was 7.04-20.84%, the average content was 13.2%, and standard deviation was 2.6%. The germplasms distribution was composed of a suitable group for the preparation of the calibration formula because the content distribution was a normal, excluding the 13.0-15.5% content section. In order to verify the applicability of the NIRS prediction model, we measured the crude protein content of the 300 wheat germplasms that were not used for the calibration using both Kjeldahl analysis and NIR spectrum. The analysis value calculated using each method were statistically processed, and the test results and statistical indicators of the predictive model were compared. As a result, The R² value of the optimized NIRS prediction model was 0.997, and the Standard error of Calibration value(SEC) was 0.132, and slope value was 1.000. With prediction model selection, compared to Kjeldahl method, R² values were 0.994(Kjeldahl), 0.998(NIRS), and the SEC value were 0.191 and 0.132, respectively, comparing the statistical indices of the forecast model. And slope value were 1.013, 1.000, respectively. The analysis of crude protein content by the NIRS predictive model developed by each statistical index showing similar figures is judged to show a high degree of correlation with the Kjeldahl analysis. The proven calibration equation will be used to measure the crude protein content of wheat germplasms held by the National Agrobiodiversity Center, and by dividing the wheat germplasms by their use according to the crude protein content, it will provide useful information to relevant researchers.

• Journal of Science Education
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• v.48 no.2
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• pp.91-100
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• 2024

The use of smart devices in science classes has brought about positive changes, such as increased student participation and more self-directed learning. Smart devices are increasingly being used in science classes, creating a need to develop lesson models that can stimulate students' interest and encourage active, self-directed learning in scientific inquiry and experimental activities. In smart education, smart devices and applications play a major role. However, in the "Mixture Separation" section of middle school science, chromatography focuses mainly on paper chromatography, which is not currently used in the field of actual research. This approach is not well-suited for students preparing for a new future society, and it is becoming obsolete due to curriculum revisions. Although chromatography can be used as an activity for career exploration, removing it is not convincing. The advantage of using thin-layer chromatography (TLC), which is employed in actual research, is that it is inexpensive and easy to use in classroom settings. In this study, we have developed a new, faster, and simpler analysis method for TLC that uses smart devices for both qualitative and quantitative analysis. We hope this method will enhance student engagement and facilitate small-scale learning by integrating smart devices into learning activities, making it a practical tool for actual school settings.

• Journal of Korean Society of Steel Construction
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• v.10 no.3 s.36
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• pp.509-523
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• 1998

A consistent finite element formulation and analytic solutions are presented for stability of thin-walled circular arch. The total potential energy is derived by applying the principle of linearized virtual work and including second order terms of finite semitangential rotations. As a result, the energy functional corresponding to the semitangential moment is newly derived. Analytic solutions for the out-of-plane buckling of symmetric thin-walled curved beam subjected to pure bending or uniform compression with simply supported boundary conditions are obtained. For finite element analysis, the cubic Hermitian polynomials are utilized as shape functions and $16{\times}16$ stiffness matrix for curved beam elements and $14{\times}14$ stiffness matrix for straight beam elements are evaluated, respectively. In order to illustrate the accuracy of this study, analytical and numerical results for lateral buckling problems of circular arch are presented and compared with available analytical solutions.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.1
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• pp.105-117
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• 1994

A finite element procedure which can trace plastic collapse behavior of plane frame structures under small and large deformation is presented. The member is assumed to be prismatic and straight, and has the rectangular or I cross section. For the elasto-plastic analysis, the concept of plastic hinge is introduced and the incremental displacement method is applied. The limit state condition of the plastic hinge is considered under the combined condition of a bending moment and an axial force. Numerical examples are presented in order to demonstrate the validity and efficiency of the proposed procedure.