• International conference on construction engineering and project management
• /
• 2009.05a
• /
• pp.658-668
• /
• 2009

Earth-moving operation has a great impact on the overall budget and schedule of any heavy civil projects. More often than not, the operational decisions are made largely based on field personnel's experience and judgment. In particular, decisions on earth moving operations by scraper-dozer fleets have been heavily influenced by the following belief: "The longer a dozer pushes a scraper for loading, the better earth-moving productivity is gained by the fleet." Even though there is some truth to this notion, scraper-dozer earth moving operations involve a much complex process that requires a systematic analysis for predicting the maximum production. To this end, this paper presents a spreadsheet-based scraper-dozer fleet operation model for its production optimization. Various optimization techniques, including a genetic-algorithm method, are presented for comparison and each technique's pros and cons are discussed.

• Proceedings of the KSRS Conference
• /
• 2004.10a
• /
• pp.598-600
• /
• 2004

In Europe most Earth Observation (EO) data users rely on several EO missions, both to increase sustainability of their service and to widen the range of observation parameters. In addition to its own missions such as ERS 1 &2, ENVISAT and the Earth Explorers, ESA therefore offers access to the scientific and applications community to so-called 'Third Party Missions'. Third Party (TP) missions are complementing the observations of ESA missions, are used to prepare for future ESA missions including cross-calibration and create synergy to favor a wider use of EO data within ESA Member States.

• Korean Journal of Remote Sensing
• /
• v.38 no.5_3
• /
• pp.863-872
• /
• 2022

Rare earth elements (REEs) have been used as one of power tracers for understanding geological and environmental changes due to their similar physico-chemical properties. In this study, we investigated the characteristics of rare earth elements in atmospheric particulates(PM_2.5) collected in Beijing and Gwangju during January 2018. The total concentrations of REEs in the Beijing samples were about 16X higher than those in Gwangju samples, and both samples are enriched in light REE than heavy REE, up to 8-10 times. The Post Archean Australian Shale (PAAS)-normalized pattern showed that both samples are enriched in Eu, Tb, and Er, and displayed positive Eu but negative Ce anomalies. The elemental correlations indicate that both samples originated from China desert and Loess plateau as well as cities surrounding Beijing. This study suggests that REEs in PM_2.5 can be used as a powerful proxy of revealing the difference between China and Korea, and provide basic information on the source and transport of PM_2.5.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2005.03a
• /
• pp.1461-1467
• /
• 2005

In this study, a new earth retention system has been developed and introduced. This system is a self-supported earth retaining wall without struts. The new earth retention system consists of connected double H-pile and wale. This system provides a larger spacing of support, economical benefit, construction easiness, good performance and safety. This paper explains basic principles and mechanism of self-supported earth retaining wall. In order to investigate applicability and safety of this system, numerical analysis was performed. The finite differential method program, FLAC3D is used. The predicted performances of this system were presented and discussed.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.28 no.2
• /
• pp.63-73
• /
• 1986

The model was developed by applying the principles of Bacot and Vidal to measure the behavior of deformation of the reinforced earth wall, and various tasts were performed by using the plastic fabric filter and the galvanized steel plate as a strip. The results obtained are as follows; 1. When the reinforced earth wall is deformed by the load, the strip is completely reinforced by the backfill materials and changed to the rigid block state, under the state of failure which permits sliding only, the next theoretical equation is formed. (H/L) . tan$\theta$ [cosO-sinOtanO] =2sinO[tan($\theta$ +0) +tanO] 2.The degree of the mutual reinforcement of the backfill material and the strip depend on the physical characteristics of the each material especially the angle of shearing resistance of the backfill material is desirable over 20$^{\circ}$ and, if it is over 400, its function could be a maximum. 3.The distribution of the maximum tensile strain of the reinforcement is changing with the height of reinforced earth wall, and when the height from bottom of the reinforced earth wall is 1.85 to 3. 35m, the maximum tensile strain appears at 2m from the skin element. The maximum tensile strain is increased by the depth of the reinforced earth wall from surface, and increased with the lapse of time after construction. 4.The failure surface of the reinforced earth wall by the concrete skin was about 60$^{\circ}$and the failure behavior of the reinforced earth wall in which the fabric filter was buried was slow, and so the pore pressure could be decreased. 5.It is possible to construct the fabric retained earth wall by the plastic fabric filter only. And the reinforcing effect between the steel plate and the plastic fabric filter is not largely different. however, in the aspect of the economic durability, the plastic fabric filter is more advantageous. 6.The reinforcing action mainly depends on the width and the length of the reinforcing materials, if possible, the full width is advantageous to enlarge the contact area with backfill. but considering the economic aspect, it is neccessary to develop the method controlling the space of the strip.

• Earthquakes and Structures
• /
• v.18 no.4
• /
• pp.423-435
• /
• 2020

An accurate evaluation of structural damage is essential to performance-based seismic design for the structure across the earth fissure. By comparing the calculation results from three commonly used damage models and the experimental results, a weighted combination method using Chen model was selected in this paper as the seismic damage evaluation. A numerical model considering the soil-structure interaction (SSI) was proposed using ABAQUS software. The model was calibrated by comparing with the experimental results. The results from the analysis indicated that, for the structure across the earth fissure, the existence of earth fissure changed the damage distribution of the structural members. The damage of structural members in the hanging wall was greater than that in the foot wall. Besides, the earth fissure enlarged the damage degree of the structural members at the same location and changed the position of the weak story. Moreover, the damage degree of the structure across the earth fissure was greater than that of the structure without the earth fissure under the same excitation. It is expected that the results from this research would enhance the understanding of the performance-based seismic design for the structure across the earth fissure.

• Journal of The Korean Association For Science Education
• /
• v.33 no.3
• /
• pp.639-649
• /
• 2013

The purpose of this study is to figure out how teachers conduct an experiment in measuring the size of the Earth and how students recognize it. For this study, an in-depth interview was conducted one week after the lesson on the experiment about measuring the size of the Earth. The participants were five secondary school teachers and five secondary school students. The in-depth interview was recorded and transcribed. The result of the interview was drawn through an inductive categorized analysis method. As a conclusion of this study, the teachers taught the students the lesson using alternate angles instead of using the altitude of the Sun. Their lessons were based on Eratosthene's story or some related illustrations suggested in the textbook and not based on an explanation of the principle. Also, students measured the Earth's size only by using alternate angles and didn't understand the meaning of the shadow in the experiment. The results of this study show that teachers need to reconstruct the textbook and understand the accurate experimental principle for the students to have a meaningful experience of the experiment on measuring the size of the Earth.

• The Bulletin of The Korean Astronomical Society
• /
• v.28 no.2
• /
• pp.56-56
• /
• 2003

• The Bulletin of The Korean Astronomical Society
• /
• v.30 no.1
• /
• pp.63.1-63.1
• /
• 2005

• The Bulletin of The Korean Astronomical Society
• /
• v.30 no.1
• /
• pp.63.2-63.2
• /
• 2005