• Journal of the Korean Geosynthetics Society
• /
• v.16 no.3
• /
• pp.21-30
• /
• 2017

Cement grouting method is generally applied for the purpose of reinforcement of deteriorated reservior. Problems have been raised due to the limit of the injection material. In order to solve these problems, various grout materials have been developed. However, there are many cases in which the grounds are disturbed in actual field. In this study, the physical properties of hybrid grout with high fineness and high viscosity characteristics were analyzed to enable penetration into the ground. Optimum inflation agent was selected and mixed with the grout. The pressure and compaction effect on expansion was examined and its effectiveness was verified. From the result of confirming expansion ratio, uniaxial compressive strength, expansion pressure and compaction effect, the HI-E (2%) sample was analyzed to be excellent in improvement effect by the inflation agent. Hence, hybrid grout can be effectively applied for the impermeable and reinforcement method of deterioration reservoir and tide embankment.

• Journal of the Korea Convergence Society
• /
• v.9 no.4
• /
• pp.151-160
• /
• 2018

Waxes currently used as a coating material to preserve surfaces of outdoor iron sculptures tend to face lower coating strength and efflorescence due to the aging from air pollution and acid rains. Consequently, they are subjected to repeated corrosions shortly after the treatment. And the sculptures face the problem losing their original nature because of the changes of colors and lusters, so this convergence study aims at developing wax with better performance than the existing materials. For this reason, the study identified the effects of physical property using the environmental experiments such as the tests of salt spray and gas corrosion as well as the analysis of luster level and thermo-gravimetry. As this study result, the developed ISC wax showed the excellent blocking effect from salt water and coating durability more than five times compared with the existing waxes, better acid resistance by two-four times, sun block effect by 2-10 times, improved luster variance by 3-16 times, improved thermo-stability and durability by 0.5-5 times, and therefore demonstrating far better coating effect than the existing waxes. In the light of these findings, this study contributes for this new development which can replace the existing waxes used so far in order to preserve the outdoor iron sculptures.

• Korean Journal of Soil Science and Fertilizer
• /
• v.33 no.6
• /
• pp.453-462
• /
• 2000

This study was carried out to know the effect of urea addition for composting of paper mill sludge(PMS). For the purpose. PMSs containing 0%, 1.5%, 3%, and 6% urea were composted at aerated static pile(ASP) for about 80day periods. During the composting, the basic physical, chemical, and biological parameters such as temperature, color. C/N ratio, cation exchange capacity, and phytotoxic test were investigated. From the measurement of the parameters, 0~3% urea-containing PMS except for 6% urea-containing PMS showed to be normally stabilized. Thus among these treatments, 0% and 3% urea-containing PMS were applied at agitated bed system(ABS), a pilot plant of a large scale, to evaluate the possibility of practical use. Considering to the changes of the parameters investigated during composting in ASP and ABS, PMS showed to be successfully stabilized in the two facilities. However, when composted with PMS and urea, even the final PMS compost stabilized for a period enough brought out the bright grayish color. So it may be necessary to add a subsidiary amendments such as animal manure to form brown-colored products.

• Journal of the Korean Geotechnical Society
• /
• v.28 no.4
• /
• pp.91-100
• /
• 2012

Soil-water characteristic curves (SWCCs), which represent a physical property in partially saturated soils, show the relation between volumetric water content and matric suction. The SWCCs exhibit hysteresis during wetting and drying, however experimental expressions used to describe SWCCs have generally ignored the hysteresis. In addition, the shape of SWCC may depend on the void ratio which is changed by soil skeleton deformations or hysteretic behavior under various loading conditions. Hence, it is necessary to understand, both empirically and analytically, the relationship between soil skeleton deformations and the SWCCs of various soils. The typical SWCCs experimentally have drying, wetting, and the second drying curve. The measurement of a complete set of hysteretic curves is severely time-consuming and difficult works, then the first drying curve of SWCC is generally determined to estimate the hydraulic conductivity and shear strength function of partially saturated soils. This paper presents the hydraulic-mechanical behavior of partially saturated soils (weathered soil and silty soil) for volume changes and hysteresis in SWCCs regarding the difference between the first drying and wetting curve.

• Journal of The Korean Association For Science Education
• /
• v.41 no.4
• /
• pp.283-295
• /
• 2021

This study attempts to explore the nature of science anxiety experienced by science-gifted middle school students based on Giorgi's phenomenological research method. Among the first-year middle school students selected by the University-affiliated Science Education Institute for the Gifted, six science-gifted students with high levels of science trait anxiety and science state anxiety experience were selected. Two interviews related to experience of science anxiety were conducted with participants. As a result of the analysis, science anxiety experienced by science-gifted students was caused by setting the ideal self-concept, lack of confidence, past experiences, difficulty in contents, and something valuable. Students complained of physical·physiological, cognitive, emotional·psychological discomfort when they felt science anxiety, and recognized it as an opportunity for growth. In addition, science-gifted students were shown to cope with various ways such as confronting uneasy situations directly or refining their minds to overcome various uncomfortable symptoms that arise when science anxiety is triggered. Some students thought that no special efforts were required to lower their level of anxiety because anxiety was relieved over time. The students had both negative and positive meanings for science anxiety. The results of this study will help teachers in-depth understanding of middle school science-gifted students who experience science anxiety and provide a theoretical basis for what kind of educational environment should be created and educational programs should be provided in relation to science anxiety.

• Journal of the Korean Institute of Landscape Architecture
• /
• v.37 no.4
• /
• pp.32-41
• /
• 2009

Places such as famous urban sights and foreign settlements have recently been created in Korea, which reflects the increase in social and cultural exchanges and the number of place-making and landscape-planning projects. Understanding place identity is required in environmental design and planning. This paper examined the components of the identity of place through comparison of perceptions of "placeness" between residents and visitors of Seo-Rae Village, Seoul, Korea. More than 40% of French nationals in Korea reside in the village, which many Koreans visit as an urban sightseeing place. Twenty-five French inhabitants and forty-one Korean visitors were surveyed. Insideness of Seo-Rae Village was formed by limited activities and needs of the residents, primarily children's education and food purchases. Residents mentioned that the physical environment, especially buildings, lacked theauthenticity of French style. The symbolic meaning of the French village influenced the visitors' activities. The authenticity of French style, however, did not affect the perception of visitors and outsideness of the place. Visitors' activities and cognitive meanings of the place were formed mainly by the commercial environment established by Korean investments. Commercialization of the place and related activities played an important role in establishing insideness of the place. The village shows the phenomenon of the reversal of insideness and outsideness. The "placeness" of Seo-Rae village has been shaped by visitors' tastes rather than the true experience of insideness. Mass identity formed by mass media using French characteristics influenced this phenomenon. Insideness formed by inhabitants appeared to be a pseudo-place, which was created by the French tastes of visitors and lacked French authenticity. Seo-Rae Villagerepresents a superficial cloak.

• Journal of the Korean Association of Geographic Information Studies
• /
• v.6 no.1
• /
• pp.48-58
• /
• 2003

Recently in order to extinguish the large scale of forest fire efficiently and rapidly the forest fire extinguishment equipment such as helicopters and vehicles has been mobilized. In this situation, the most consideration for the effective extinguishment is to understand the forest fire surrounding area and situation very well and arrange and manage the extinguishment equipment timely. In this paper, the client/serve-based forest fire extinguishment helicopter management system was constructed by integrating GPS(global positioning system) and GIS(geographic information system) technologies. This system manages and considers not only extinguishment equipment information such as helicopters and vehicles including manpower arrangement but also extinguishment environment information such as storing reservoir status and road situation and so on. For this, the real time tracking of helicopter location was first acquired through GPS technology then all the information about forest fire surrounding area was offered through the user-friendly interface of GIS concept. The result of constructing this system helps to extinguish a large scale of forest fire rapidly and effectively within shorter time then reduces physical damage and much manpower mobilization.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.41 no.10
• /
• pp.788-795
• /
• 2013

A magnesium bipolar plate whose surface was protected by thinly deposited silver layer was investigated as an alternative to existing graphite bipolar plate of PEM fuel cells. Thin silver layer of $3{\mu}m$ was deposited on a magnesium alloy substrate by physical vapor deposition (PVD) method in an environment of $180^{\circ}C$. A number of tests were conducted on the fabricated magnesium based bipolar plates to determine their suitability for use in PEM fuel cell stacks. The test on corrosion resistance in the same pH condition as in a PEM operation demonstrated the layer protected the magnesium alloy substrate, while unprotected substrate suffered from severe corrosion. The contact resistance of the fabricated bipolar plate was less than $20m{\Omega}-cm^2$ which was superior to the conventional bipolar plates. A single cell was constructed using the fabricated bipolar plates and power output was measured. Due to the enhanced conductivity caused by low contact resistance, slight increase was observed in current density and output voltage. With low density of the magnesium substrate and ease on machining, the weight reduction of the stack of 30~40 % is possible to produce the same power output.

• Korean Journal of Ecology and Environment
• /
• v.44 no.2
• /
• pp.129-135
• /
• 2011

The possibility of nutrient removal during Scenedesmus sp. growth in Lake Paldang, Geongan cheon stream, and the outflow from a wastewater treatment system was examined. Scenedesmus sp. grew well in Lake Paldang water when total nitrogen (TN) and total phosphorus (TP) values were 1.9 and 0.02 mg $L^{-1}$, respectively, and 50% of the nutrients were removed. In Geongan cheon stream, the TN and TP was 3.0 mg $L^{-1}$ and 0.09 mg $L^{-1}$, respectively, chlorophyll-${\alpha}$ reached a maximum of 239~259 $m^{-3}$, and 50% of the nutrients were removed. In the wastewater treatment outflow, where Scenedesmus sp. already existed, the organism grew well without inoculation. Scenedesmus sp. can grow with proper inoculation and physical turbulence in natural waters, such as lake and stream water, and nutrients can be eliminated as phytoplankton growth occurs.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.21 no.12
• /
• pp.857-866
• /
• 2020

'Movement' is an expanded concept of 'place' where people act, interact with one another and achieve a specific purpose at every moment. Wheelchairs, as a mobility aid, have a profound impact on improving the quality of physical and psychological well-being for the mobility disadvantaged groups who have mobility difficulties. Such mobility aids were developed mainly for outdoor activities, but in recent years, mobility aids for indoor spaces, the main living environment, are also being developed. Because indoor mobility aids generally move short distances repeatedly, this study examined the characteristics of lithium-ion batteries in short-distance driving of battery-powered wheelchairs and compared them with the characteristics of lithium-ion batteries in continuous driving. The result showed that the driving time for short-distance driving was 2.8% shorter than that of continuous driving. The current supplied to the motor was 15.4% higher for short-distance driving than that of continuous driving.