• Journal of Electrical Engineering and Technology
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• v.4 no.1
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• pp.143-148
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• 2009

About 70% of Korea consists of mountainous areas, and during the construction of many roads and railroads, cut slopes are inevitably formed. The rainy season, frost heaving in winter, and thawing in spring can all cause rockfalls and landslides. The failure of these slopes is increasing every year, causing damage to vehicles, personal injury and even death. To protect people and property from such damage, a real-time monitoring system is needed to detect the early stages of slope failures. The GMG placed TRS sensor units in the slopes to monitor them in real-time. But due to its reliance on data lines and power lines, the system is vulnerable to lightning damage. The whole system can be damaged by a single lighting strike. Consequently, for the purposes of this paper we propose the use of the Ubiquitous Sensor Network (USN) which follows the IEEE 802.1.4. By using the USN system we can minimize lightning damage and can monitor the movement of the slopes consistently.

• Journal of Korean Society of societal Security
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• v.1 no.2
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• pp.61-66
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• 2008

More than 70% of Korea consists of mountainous area and during the construction of roads and railroads many cut-slopes are inevitably formed. A number of environmental factors, such as the rainy season and frost heave during winter/thaw during spring, can result in rock falls and landslides. The failure of slopes is increasing every year and can cause damage to vehicles, personal injury and even fatality. In order to help protect people and property, there is a need for real-time monitoring systems to detect the early stages of slope failures. In this respect, the GMG has been using Translation Rotation Settlement (TRS) sensor units installed on slopes to monitor movement in real-time. However, the data lines of this system are vulnerable and the whole system can be damaged by a single lightning strike. In order to overcome this, GMG have proposed the use of Ubiquitous Sensor Networks (USN). The adoption of a USN system in lieu of data cables can help to minimize the risk of lightning damage and improve the reliability of slope monitoring systems.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.605-608
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• 2008

This study investigated fundamental properties corresponding to mixtures for the high strength, and their properties of spalling prevention after a fire test. The results were summarized as following. For the flowability of using mixtures for the high strength, the target flow was satisfied with a small quantity of high performance reducing water agent to compare with silica fume. For the compressive strength in the case of using mixtures for the high strength, it was higher to compare with silica fume at 7 days, so it was proved that using mixtures for the high strength was profitable to prevent early frost damage. The compressive strength at the 28 days of silica fume and mixtures for the high strength were similar. There was no reduced tendency at the compressive strength according fiber contents, so it found out that the bonding strength between the fiber and concrete was hardly effective. For the spalling properties, the specimens without fibers were destroyed, however using over 0.05% of NY and PP fibers was effective to prevent spalling on the high strength concrete.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.5
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• pp.59-66
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• 2013

Because ordinary concrete cannot be hardened well under sub-zero temperatures, anti-freeze agents are typically added to prevent the frost damage and to ensure the proper hardening of concrete. With the advantage of a rapid exothermic reaction property, jet set concrete may be used as a cold weather concrete because it can reach the required strength before being damaged by cold weather. Recent studies are reported that magnesia-phosphate composites can be hardened very quickly and hydrated even in low temperature, which can be used as an alternative of severe cold weather concrete in arctic regions. This study developed the magnesia-phosphate composites that can be used in severe cold regions and suggested an appropriate mixture design from the experimental results.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.6
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• pp.163-170
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• 2012

With the advantage of a rapid exothermic reaction property, jet set concrete may be used as a cold weather concrete because it can reach the required strength before being damaged by cold weathers. And it can be hardened more quickly if the field temperature is properly compensated by heating. Because ordinary concrete cannot be hardened well under sub-zero temperatures, anti-freeze agents are typically added to prevent the frost damage and to ensure the proper hardening of concrete. While the addition of a large amount of anti-freeze agent is effective to prevent concrete from freezing and accelerates cement hydration resulting in shortening the setting time and enhancing the initial strength, it induces problems in long-term strength growth. Also, it is not economically feasible because most anti-freeze agents are mainly composed of chlorides. Recent studies reported that magnesia-phosphate composites can be hardened very quickly and hydrated even in low temperatures, which can be used as an alternative of cold weather concrete for cold weathers and very cold places. As a preliminary study, to obtain the material properties, mortar specimens with different mixture proportions of magnesia-phosphate composites were manufactured and series of experiments were conducted varying the curing temperature. From the experimental results, an appropriate mixture design for cold weathers and very cold places is suggested.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.6
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• pp.427-446
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• 2008

A review on the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2006 has been accomplished. Focus has been put on current status of research in the aspect of heating, cooling, ventilation, sanitation and building environments. The conclusions are as follows. (1) The research trends of fluid engineering have been surveyed as groups of general fluid flow, fluid machinery and piping, etc. New research topics include micro heat exchanger and siphon cooling device using nano-fluid. Traditional CFD and flow visualization methods were still popular and widely used in research and development. Studies about diffusers and compressors were performed in fluid machinery. Characteristics of flow and heat transfer and piping optimization were studied in piping systems. (2) The papers on heat transfer have been categorized into heat transfer characteristics, heat exchangers, heat pipes, and two-phase heat transfer. The topics on heat transfer characteristics in general include thermal transport in a cryo-chamber, a LCD panel, a dryer, and heat generating electronics. Heat exchangers investigated include pin-tube type, plate type, ventilation air-to-air type, and heat transfer enhancing tubes. The research on a reversible loop heat pipe, the influence of NCG charging mass on heat transport capacity, and the chilling start-up characteristics in a heat pipe were reported. In two-phase heat transfer area, the studies on frost growth, ice slurry formation and liquid spray cooling were presented. The studies on the boiling of R-290 and the application of carbon nanotubes to enhance boiling were noticeable in this research area. (3) Many studies on refrigeration and air conditioning systems were presented on the practical issues of the performance and reliability enhancement. The air conditioning system with multi indoor units caught attention in several research works. The issues on the refrigerant charge and the control algorithm were treated. The systems with alternative refrigerants were also studied. Carbon dioxide, hydrocarbons and their mixtures were considered and the heat transfer correlations were proposed. (4) Due to high oil prices, energy consumption have been attentioned in mechanical building systems. Research works have been reviewed in this field by grouping into the research on heat and cold sources, air conditioning and cleaning research, ventilation and fire research including tunnel ventilation, and piping system research. The papers involve the promotion of efficient or effective use of energy, which helps to save energy and results in reduced environmental pollution and operating cost. (5) Studies on indoor air quality took a great portion in the field of building environments. Various other subjects such as indoor thermal comfort were also investigated through computer simulation, case study, and field experiment. Studies on energy include not only optimization study and economic analysis of building equipments but also usability of renewable energy in geothermal and solar systems.