• Geomechanics and Engineering
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• 제23권3호
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• pp.207-215
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• 2020

This paper presents a kinematic limit analysis for passive earth pressure of rigid retaining structures considering the unsaturation of the backfill. Particular emphasis in the current work is focused on the effects of the spatial change in the degree of saturation on the passive earth pressure under different steady-infiltration/evaporation conditions. The incorporation of change of effective unit weight with degree of saturation is the main contribution of this study. The problem is formulated based on the log-spiral failure model rather than the linear wedge failure model, in which both the spatial variations of suction and soil effective unit weight are taken into account. Parametric studies, which cover a wide range of flow conditions, soil types and properties, wall batter, back slope angle as well as the interface friction angle, are performed to investigate the effects of these factors on the passive pressure and the corresponding shape of potential failure surfaces in the backfill. The results reveal that the flow conditions have significant effects on the suction and unit weight of the clayey backfill, and hence greatly impact the passive earth pressure of retaining structures. It is expected that present study could provide an insight into evaluation of the passive earth pressure of retaining structures with unsaturated backfills.

• 한국지구과학회지
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• 제24권5호
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• pp.371-377
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• 2003

The purpose of this study is to examine the effects of utilizing concept maps in a rock-related unit. To do this, two groups composed of 73 sixth grade students engaged in this study. One group (experimental group) participated in utilizing concept maps in the unit, the other (control group) took part in traditional instruction in the same unit. The results of this study are as follows, after seventeen sessions: First, the achievement between the two groups showed significant difference. It indicates that utilizing concept maps as an instructional method is effective. Second, in the examination of the experimental group's attitudes toward concept maps, the students showed more affirmative responses on cognitive items than on affective items. Third, the students showed that they have difficulty in the method and the procedure of drawing up the concept maps. It indicates that the method and the procedure are sufficiently learned before instruction begins.

• 한국지구과학회지
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• 제30권4호
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• pp.513-526
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• 2009

해양 염분의 단위가 퍼밀(%o)에서 다른 단위로 바뀐 지 오랜 세월이 지났다. 하지만 우리나라 중학교, 고등학교 과학 및 지구과학 교과서는 여전히 오래 전에 정의한 염분 단위인 퍼밀(%o)을 사용하고 있다. 본 연구의 목적은 염분단위의 변화와 측정 기술에 대한 역사적 발달 과정을 개괄적으로 다루고, 염분 단위들 사이의 차이를 제시하며, 그리고 교과서에서의 염분 단위 수정에 대한 필요성과 타당성을 강조하는데 있다. 이를 위해 제 7차 교육과정에 기초한 27종의 중등 과학교과서에서 다루고 있는 염분 단위의 표현, 염분의 정의들을 조사하였다. 분석 결과는 1967년부터 2008년까지 한국해양학회지에 게재된 논문들에서 사용하고 있는 염분 단위 사용의 빈도수와 비교하였다. %o 사용의 백분율은 교과서 본문에서 96.3%, 그림과 표에서 83.8%에 달하였다. 이에 반해 과학적 논문들은 1994년부터 psu를 사용하기 시작하였으며, 2004년 이후로는 %o을 거의 사용하지 않고 있었다.

• 한국농공학회지
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• 제23권1호
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• pp.86-102
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• 1981

The soil test data of 28 earth dams, scheduled to be constructed in Kore3, were selected for this study. The safety factors of their side slops were computed using Fellenius' "slice Method" by computer. The results summarized in this study are as follows; 1. Dam sections can be easily determined by fig.10 without a time consuming trial and error calculations of assumed sections. 2. For the economical design of earth dam sections, it was found that more cohesive soil was suitable for lower dams(dam height less than 25m) and soils with a higher friction angle was better for higher dams 3. In the case that used soil materials have the same Internal friction angle, side slope increase was almost same. 4. The relationship between side slope and friction angle was found as log.S=a tan ø+b (Fig. 7) 5. The relationship between side slope and cohesion (c) was also found as log. S=a c+b (Fig. 8) 6. The change of safety factors due to the change of central core materials was very little (Table-2) 7. The decrease of safety factors according to the unit weight increase of embankment materials was negligible. 8. In general the relationship between the wet unit weight and the saturated unit weight was r sat = (rt)$^2$+0. 140. This study will contribute to the determination of economic and safe planning and designing of earth dams, embankments and cutting side slopes.

• KIEAE Journal
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• 제13권6호
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• pp.137-143
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• 2013

The purpose of this study is to suggest optimum micro-filler experiment method to select the optimal particle size of earth for using in earth construction works and test this suggestion through compressive strength measurement. According to the results of selecting the method to choose the optimum micro-filler mixing of earth and sand, three-stage filling(plate tamping) showed relatively high results and so was estimated to be the proper filling method. According to the results of optimum micro-filler experiment of earth and sand by the maximal sizes of sand, between 80% and 90% showed the highest result values. The larger the maximum size of sand was, the lower the addition ratio of sand was in optimum micro-filler mixing. According to the results of compressive strength experiment by the particle sizes of earth and sand, 90% in the addition ratio of sand showed the highest results, and so tended to be similar to the results of unit volume weight experiment.

• 한국지구과학회지
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• 제41권4호
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• pp.405-414
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• 2020

In this study, we analyzed the development of high school students' argumentation through their writings on socio-scientific Issues (SSI) related to the Climate Change Unit in the Earth Science I curriculum. Pre- and post-writing assignments on the two main causes of global warming were analyzed and compared. In addition, an in-depth interview of the focus group was conducted with 7 students who showed a distinct change in the level of argumentation. According to the results, 16 of 52 students remained at the same argumentation level in pre- and post-writing assignments, and students remaining at Level 2 among five levels had difficulty in understanding the Toulmin's argument pattern (TAP) structure. Using the TAP structure, 29 of 52 students demonstrated increased argumentation levels in the post-writing assignments. The conclusions include that writing lessons on SSI using the TAP in Earth science classes can improve the level of high school students' argumentative writing, and that the level of students' argumentation can develop with the elaboration of their level of falsification. Also, it is suggested that the science curriculum should increase students' science writing competencies by specifying science writing as one of the goals.

• 한국지구과학회:학술대회논문집
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• 한국지구과학회 2005년도 추계학술발표회 논문집
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• pp.323-330
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• 2005

본 연구에서는 제7차 교육과정의 고등학교 지구과학Ⅰ,Ⅱ 교육과정의 내용 체제와 과학관의 전시내용을 비교 분석하여 과학관이 교육과정의 성격과 목표를 얼마나 잘 반영하고 있는가를 알아보았다. 본 연구의 결과는 다음과 같다. 첫째, 교육과정 상의 지구과학 내용이 전시되어 있는 영역이 50% 이하이고 단원별로 편중되어 있다. 둘째, 과학관의 지구과학 교육과정 반영 정도는 보통이다.(5점만점의 2.8점) 셋째, 유의수준 0.05하에서 과학관별 전시내용 평균점수는 차이가 있고, 단원별로는 차이가 없다.

• 대한지구과학교육학회지
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• 제8권1호
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• pp.76-86
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• 2015

The purpose of this study is to take advantage of the smart teaching - learning programs about the unit of 'Earth and Moon' and find out how to apply the effect appears. Teaching-Learning program was conducted over eight lessons. And we analyzed the effect of the program at any time through the evaluation and interview. The results are as follows. First, this study proposed a method to assist in the teaching and learning of spatial ability for students' movement of the Earth and the Moon. The program takes advantage of N-Screen Applications were configured to allow both Earth observation insider perspective and the external multilateral perspective. This improves students' understanding qualitatively. Second, we applied the teaching and learning programs utilizing smart smart devices, and the result was a lot of low rank students' average score rises. In addition, we were able to see that many students' understanding and interest, self-confidence are improved.

• Ocean and Polar Research
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• 제36권4호
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• pp.383-394
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• 2014

The surface sediments from the manganese nodule exploration area of Korea in the Clarion-Clipperton fracture zone were investigated to understand the resource potential of and emplacement mechanism for rare earth elements (REEs). The sediments are categorized into three lithological units (Unit I, II and III from top to bottom), but into two groups (Unit I/II and Unit III) based on the distribution pattern of REEs. The distribution pattern of REEs in Unit I/II is similar to that of Post-Archean Australian Shale (PAAS), but shows a negative Ce anomaly and enrichment in heavy REEs (HREEs). In Unit III, the HREE enrichment and Ce anomaly is much more remarkable than Unit I/II when normalized to PAAS, which are interpreted as resulting from the absorption of REEs from seawater by Fe oxyhydroxides that were transported along the buoyant plume from remotely-located hydrothermal vents. It is supported by the PAAS-normalized REE pattern of Unit III which is similar to those of seawater and East Pacific Rise sediments. Meanwhile, the PAAS-normalized REE pattern of Unit I/II is explained by the 4:1 mixing of terrestrial eolian sediment and Unit III from each, indicating the much smaller contribution of hydrothermal origin material to Unit I/II. The studied sediments have the potentiality of a low-grade and large tonnage REE resource. However, the mining of REE-bearing sediment needs a large size extra collecting, lifting and treatment system to dress and refine low-grade sediments if the sediment is exploited with manganese nodules. It is economically infeasible to develop low-grade REE sediments at this moment in time because the exploitation of REE-bearing sediments with manganese nodules increase the mining cost.

• 한국측량학회:학술대회논문집
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• 한국측량학회 2003년도 추계학술발표회 논문집
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• pp.169-174
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• 2003

Design of a rational earth volume conversion coefficient is required as the earth volume conversion coefficient may give great influence on construction work volume and construction costs in the civil engineering works where large-scaled earth volume is excavated. However, there are a great deal of difficulties in the calculation of the exact spoil surface earth and Insufficient earth volume by adopting the figures presented on the generally used design specifications which are not the results obtained from the selection tests in calculating the earth volume conversion coefficient. In this connection, it would be desirable to calculate the earth volume conversion coefficient by carrying out large-scaled site test adequate for the relevant environment. In consequence, this study aims at calculating the exact earth volume conversion coefficient of cutting and banking areas of weathering rocks in large-scaled construction sites where land is being developed into home lots. For this, we have excavated the respective 20 sites of the cutting and banking areas in the said site and then calculated the volume after the excavation. As a result, the relative exactness degree of the crossing was calculated at 0.5% in average. The relative exactness degree of 0.5% in the volume may be judged as an exact measurement as it corresponds to 0.17% of the relative exactness degree in the length measurement. We have calculated the exact earth volume conversion coefficient by the use of function ratio as per the wet unit weight and the indoor soil quality test as per volume calculated. And then we have found out minor differences as a result of the comparison and analysis with the earth volume conversion coefficient determined by the dry unit weight test as per sand replacement method. This may be judged as a rational design method for the calculation of earth volume conversion coefficient, as well as high reliability of site test as a precision photogrammetry is adopted for volume measurement of the irregular excavating areas.