• Journal of the Korean Geotechnical Society
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• v.15 no.1
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• pp.99-112
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• 1999

By using 92 values of lateral earth pressure coefficient(K) measured in Korea, the tendency of K with varying depth is analyzed and compared with the range of K defined by Hoek and Brown. The horizontal stress is generally larger than the vertical stress in Korea : About 84 % of K values are above 1. In this study, the theory of elasto-plasticity is applied to analyze the variation of K values, and the results are compared with those of numerical analysis. This reveals that the erosion, sedimentation and weathering of earth crust are important factors in the determination of K values. Surface erosion, large lateral pressure and good rock mass increase the K values, but sedimentation decreases the K values. This study enable us to analyze the effects of geological processes on the K values, especially at shallow depth where underground excavation takes place. A neural network expert system using multi-layer back-propagation algorithm is developed to predict the K values. The neural network model has a correlation coefficient above 0.996 when it is compared with measured data. The comparison with 9 measured data which are not included in the back-propagation learning has shown an average inference error of 20% and the correlation coefficient above 0.95. The expert system developed in this study can be used for reliable determination of K values.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.6D
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• pp.793-801
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• 2011

Existing specifications of road pavement require contractors to meet only materials and construction conditions regardless of pavement life. There are limitation of developing road pavement technology and possibility causing dispute between ordering organization and contractor with this type of specification. Research efforts to introduce performance warranty contracting are in progress in the field of road pavement to improve the problems. The performance warranty contracting gives the contractors opportunity to select materials and construction methods as they like. But they should satisfy a certain level of performance during a given period. The performance indicator and threshold value of pavement which are main elements of the warranty specification should be defined first to introduce the performance warranty contracting successfully. In this study, the performance indicator, threshold value, and warranty duration of asphalt pavement were investigated by reviewing literatures on performance warranty contracting of some states of the US. Major distresses influencing the performance of the asphalt pavement were investigated at 24 national expressway lines and national highway lines in 16 regions, and the data were analyzed to be compared to the cases of the US. Development of rational performance warranty specification for domestic asphalt pavement is expected based on the research results.

• Journal of Science Education
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• v.35 no.2
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• pp.250-261
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• 2011

The purpose of this study is to analyze how the content elements of the environment education are displayed between related subjects in elementary school curriculum and find a desirable direction of the environment education. Major subjects that handle the components of the environment education include science, physical education, social studies, ethics, and practical arts. Among these subjects, science aims for the ecological perspective, social studies aims for rational decision making and practical behaviors, and ethics aims for the correct formation of environmental ethics and values. In the component ratio of the environment education, the domains of the natural environment, environmental ethics, environmental pollution, environmental protection and measure were higher. In the formation of content elements according to grades, the connectivity of the environment curriculum has been relatively well secured in the order of the learning about the environmental components, awareness on environmental problems and the measures and efforts to overcome environmental problems. Based on the findings above, the followings are proposed for future environment curriculum in elementary school. First, it is necessary to increase the ratio of the ecological perspective based on science and coordinate the period to suggest this contents. Second, it is necessary to complement the contents of social studies regarding green growth and sustainable development which have become global issues in the environment education. Third, Pan-curriculum and integrated discussions to prepare multi-academic and interdisciplinary environment curriculum have to be preceded and through this process it is necessary to set the target of environment education and select the content elements of the curriculum.

• Journal of The Korean Association For Science Education
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• v.30 no.4
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• pp.472-486
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• 2010

The surveys for public awareness in relation to socio-scientific issues (SSI) have been limited to several topics such as public perception of risks about the issues and preference for some policies. To illuminate the public science culture literacy about SSI from a holistic perspective, this study aimed to develop an indicator system. For this purpose, the issue on climate change, which is currently one of the biggest issues worldwide, was adopted as a specific SSI and the framework centering on climate change was developed. Science culture literacy about SSI was defined as a lifestyle to identify SSI from various viewpoints and to cope with problems related to SSI appropriately. In the framework proposed, individual science culture indicators are divided into Potential and Activity area. The Potential consists of categories of Interest, Opinion and Understanding, whereas the Activity is composed of categories of Learning and Practice. To examine the reliability and validity of this framework statistically, the developed questionnaire was reviewed by science educators, environment experts and atmospheric scientists and was used to asked 777 secondary students. Based on the results of statistical analyses, the framework was modified and it consequently had 2 areas, 5 categories, 15 sub-categories, 34 indicators and 63 items. It is expected that the framework of science culture indicators for SSI could be used as a measurement tool for public awareness about various SSI topics.

• Journal of the Korea Convergence Society
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• v.11 no.6
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• pp.237-248
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• 2020

The purpose of this study is to measure the agricultural product market efficiency of the three e-commerce platforms from the perspective of consumer price fairness perception, analyze the quality and price gap of invalid brands, and help agricultural products enterprises to formulate reasonable price strategies. The characteristics of farm products sold in e-commerce platforms(quality, origin, taste, safety level) were selected as output indicators and the prices of products were selected as input indicators to evaluate the efficiency of the market through DEA analysis. According to the analysis, JD mall has the largest proportion of effective brands, while YHD.com has the highest average market efficiency, and northeast rice has the largest difference in average efficiency among the three platforms. The results show that price inefficiencies still exist in the electronic market. The development of online market for agricultural products should pay attention to consumer price fairness and pay attention to the coordination between price and quality. The limitation of this paper is that it does not focus on the influence of words of mouth marketing in internet market and consumer experience, which can be the future research direction.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.2
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• pp.713-720
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• 2013

The objectives of this study are to identify whether the small area variation also exists in the oriental medicine and, if it exists, what causes, to expand our boundary of research interests on the small area variation observed at the western medicine toward the oriental medicine as one of the fundamental research foundations and to provide any fundamental findings from this study results to the healthcare politicians to promote consumer's rational behaviors for the use of healthcare. This study analyzed the health insurance claim data (2010, 2011) which were the patients of western medicine and the outpatients of the oriental medicine with the top 10 most frequent diseases and looked into the variation of healthcare utilization among the areas after grouping resident area into an 86-area category. The study result shows that the small area variation was also observed at the part of the oriental medicine in which the characteristics of patients critically affect the healthcare expenditure per visit day rather than those of providers and the characteristics of both patients and providers equally affect the healthcare expenditure per patient. Therefore, this study suggests that government set up healthcare policies on the standardization of oriental medicine to prevent its over-utilization and unmet need, enforcing the roles of oriental medicine in the markets, enhancing the appropriate health care utilization, and expanding provision and sharing the health care information to reduce unnecessary health care utilization.

• Journal of the Korean Institute of Landscape Architecture
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• v.39 no.5
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• pp.48-56
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• 2011

The objective of this study is to develop quantitative criteria for setting reasonable standards and regulations for building heights in collective facility districts inside national parks or those connected to their borders. Heights of all building sin collective facility districts were simulated in order to determine heights of ridge lines of sight passing the upper parts of buildings from a main view point. Where a facility's zone is located at the inside or boundary of inland mountainous national parks, and there are coastal type national parks with mountains in the background, the study recommended assigning the maximum allowable height of a building as 8.82m if national park authorities intend to preserve the ridges at three-tenths the height of a mountain. It amounts to 3 or 3.5 stories when it is converted into the number of floors. It is desirable to apply this standard to accommodations like a hotel except lodge or cottage as the maximum allowable height of a building. Nevertheless, when there aren't back mountainous areas among coastal-type national parks, there is a need for applying a separate standard. If an equal and uniform standard is applied to all collective facility districts, it becomes difficult to address local differences when managing landscape. There must be flexibility when applying a standard, depending on variables such as location of view points, differences in the methods of selection of view points, and differences in view angles, etc. Thus, there is a need for different landscape management strategies that address the unique natural environment of different zones.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.11
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• pp.914-921
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• 2017

The experimental research on a high-altitude environment simulation of space launch vehicle is important for securing independent technologies with launching space vehicles and completing missions. This study selected an altitude of 65 km for the experiment environment where it exceeded Mach number of 6 after the launch of Korean Space Launch Vehicle(KSLV-II). Shock tunnel was used to replicate the flight condition. After flow establishment, in order to confirm aerodynamic characteristics and normal and oblique shockwaves, the flow verification was carried out by measuring stagnation pressure and heat flux of a forebody model, and shockwave stand-off distance of a hemispherical model. In addition, a shock-free technique to recover free-stream condition has been developed and verified. From the results of the three verification tests, it was confirmed that the flow was replicated with the error of about ${\pm}3%$. The error between the slope angle of inclined shockwave of the scaled down transition section model using the shock-free shape and the slope angle of the horizontal plate model, and between the theoretical and the experimental value of the static pressure of the model were confirmed to be 2% and 1%, respectively. As a result, the efficiency of the shockwave cancellation technique has been verified.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.5 no.2
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• pp.11-18
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• 1985

A row of bored piles has been used in several excavation works to retain the earth. This excavation bracing system has much effect on low-vibration and low-noise during construction. The system is also effective to provide protection to the adjacent existing ground and structures. For the purpose of establishment of a logical design method for the bored piles, first, a theoretical equation to estimate the resistance of piles is derived. Because arching action of soils between piles is considered in the equation, the characteristics of soils and the installation condition of piles would be considered logically from the beginning. Then a method is investigated to decide the interval ratio of piles. According to the method, the interval between piles can be decided from the information of the Peck's stability number, the coefficient of lateral earth pressure and the internal friction angle of soil. Finally, a design method is presented for the bored piles used for excavation work. In the presented design method, such factors as depth of excavation, pile diameter, interval between piles, pile length below bottom of excavation and pile stiffness, can be selected systematically.

• The Journal of Engineering Geology
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• v.18 no.1
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• pp.17-26
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• 2008

In this study, the design method of slope reinforced by the earth retention systems were systematically developed, and the flow chart of design procedure fur each system were constructed to design the slope rationally. The proposed design method is composed of 5 steps such as field condition investigation step, slope design step, landslide occurrence prediction step, slope failure scale estimation step and reinforcement countermeasure selection step. The quantitative standard of slope failure scale was established based on the arrangement of various overseas standards which is estimating the slope failure, and the analysis of slope failure scale which is occurred in the country. The slope failure scale is classified into three categories the small scale of slope failure is less than $150m^3$ of slope failure volume, the middle scale of slope failure is from $150m^3$ to $900m^3$ and the large scale of slope failure is more than $900m^3$. The earth retention system could be selected by the proposed slope failure scale based on the slope failure volume. Meanwhile, the design methods of earth retention system such as piles, soil nails and anchors were developed. The optimal countermeasure for slope stability could be proposed using above design methods.