• Journal of Surface Science and Engineering
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• v.32 no.3
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• pp.265-275
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• 1999

Titanium nitride and related overlayers produced by arc ion plating (AIP) are applied as commercial coatings in world-wide scale since the middle of 80s. Due to the achievements of low temperature deposition (LTD), they begin now to be used as wear and corrosion-resistant coatings for machine parts, besides applications on cemented carbide and high speed steel cutting tools. On the other side, TiN can be now applied successfully to brass, Al-alloy, ZnAl alloy articles as decorative coating through LTD. Various nitrides, carbonitrides, borides and other refractory compounds, such as (Ti, Al)N, TiCN, CrN, are used as the coatings for special heavy-duty working conditions instead of TiN since 90s. More and more multilayer coatings are applied now substituting single layer ones. Duplex processes are under development.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.66-71
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• 2008

Two cases with circumferential grooves were designed for a transonic compressor, and 3-D numerical simulations were conducted for stall mechanism at three representative speeds. A conclusion can be drawn from the comparison between compressors with or without casing treatment that: with the rising of rotation speed, stall margin increases dramatically under the help of casing treatments, and the case with middle grooves has reasonable compromise between stall margin increment and efficiency cutting. At lower speed, the increment reduces, and grooves at the back of blade tip have more influence on stall margin. Further investigation shows there is a transition in mechanism of compressor stall with the decline of rotational speed: at high rotation speed, the expansion of stall margin mainly results from the suppression of tip leakage vortex by casing treatments, yet it benefits more from the depression of boundary layer separation from suction surface of blade tip.

• Bulletin of the Korean Chemical Society
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• v.12 no.3
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• pp.334-342
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• 1991

To investigate the phase equilibria and structural properties of microemulsions, we study a simple phenomenological model on the basis of the cubic lattice cell with which the oil- and water-filled cells are connected one another, respectively. The surfactant is assumed to be insoluble in both oil and water, and to be adsorbed at the oil-water interface. The Schulman condition, according to which the lateral pressure of the surfactant layer is compensated by the oil-water interfacial tension, is found to hold to good approximation in the middle-phase microemulsion. Our results show that the oil- and water-filled domains in that microemulsion are about 50-150 $\AA$ across, and depend sensitively on the curvature parameters. The phase diagram is not symmetric in this model. It may be asymmetrized intrinsically by non-equivalency of oil and water. The two- and tree-phase equilibria including critical points and critical endpoints are found.

• Smart Structures and Systems
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• v.28 no.6
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• pp.839-853
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• 2021

In this paper, a novel multimode liquid metal-based pressure sensor is developed. The main body of the sensor is composed of polydimethylsiloxane (PDMS) elastomer. The structure of the sensor looks like a sandwich, in which the upper structure contains a cylindrical cavity, and the bottom structure contains a spiral microchannel, and the middle partition layer separates the upper and the bottom structures. Then, the liquid metal is injected into the top cavity and the bottom microchannel. Based on linear elastic fracture mechanics, the deformation of the microchannel cross-section is theoretically analyzed. The changes of resistance, capacitance, and inductance of the microchannel under pressure are deduced, and the corresponding theoretical models are established. The theoretical values of the pressure sensor are in good agreement with experimental data, implying that the developed theoretical model can explain the performance of the sensor well.

• Journal of the Korean Society of Marine Environment & Safety
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• v.21 no.4
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• pp.315-326
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• 2015

Temporal and spatial variations of surface water temperature in Jinju Bay for the period of 2010~2011 were studied using the data from temperature monitoring buoys deployed at 17 stations in the south coast of Korea. Water temperature shows the maximum late in January and the minimum early in August. Seasonal variation of water temperatures at the north part of the bay is smaller than the middle and the south. In summer, the lowest and the highest of maximum water temperature are distributed around Jijok Channel which is located at the south of the bay. The fluctuations of water temperatures at Noryang and Daebang Channel are smaller than others because of vertical mixing caused by passage of strong tidal currents. Wind and strong currents affect on the stratification of the surface water layer near Daebang Channel. High temperatures come in frequently around the north area when eastward constant flows appear at neap tide as blowing westerly in the springtime at Noryang Channel. Spectral analyses of temperature records show significant peaks at 7~20 day periods at Noryang Channel, 7~20 day and semidiurnal at the west coast of Changsun Island and Jijok Channel and 7~20 day and diurnal at the middle of the bay. Temperature fluctuation at Noryang Channel shows high coherence and has leading phase with those at other stations in the bay. However, the phase of temperature fluctuation at Noryang Channel falls behind that at Daebang Channel. Daebang Channel has an influence on the temperature fluctuation only at the west and middle part of the bay. Cross-correlation analyses for the temperature fluctuation show that Jinju Bay could be classified into six areas; Noryang Channel, the area of convergence and divergence at the north, Daebang Channel, the west coast of Changsun Island, the mixing area at the middle of the bay and the south inside of the bay, respectively.

• Journal of The Korean Association For Science Education
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• v.26 no.2
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• pp.200-211
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• 2006

The purpose of this study was to analyze Korean middle school student achievement in environmental science based on the TIMSS 2003 (Trends in International Mathematics and Science Study), a student comparison of 46 participating nations. Korea ranked the fourth with a mean score of 554 in environmental science. However, all 3 environment science topics assessed in TIMSS are not included in the Korean science curriculum through 8th grade, even though they are included in most other participating nations' curricula. The average percent correct of items was analyzed according to the main topic, the item type and the cognitive domain. Items that showed differences between the average percent correct of Korea and the international average as well as differences between the average percent correct of boys and girls were further analyzed. Results revealed that Korean students performed better than the international average, especially in 'use and conservation of natural resources', multiple-choice items, and items requiring 'factual knowledge'. Also, male students demonstrated significantly higher achievement than female students. On the other hand, Korean students showed relatively lower achievement in constructed-response items, items that contained content they had not learned in science lessons and items requiring descriptions of the uses and effect of science and technology. Moreover, Korean student lacked understanding about acid rain, global warming, and ozone layer destruction. Korean female students showed relatively lower environmental conceptions and lower performance on items requiring data analysis than Korean male students. On the basis of these results, this study suggested that topics of environmental science be included in the science curriculum and taught in the science classroom to help middle school students more fully comprehend environmental issues.

• Horticultural Science & Technology
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• v.34 no.2
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• pp.342-353
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• 2016

This study was initiated to evaluate green color retention under three different soil systems. Several turfgrasses were evaluated in multi-layer, USGA, and mono-layer systems. Turfgrass entries were comprised of three cultivars of Korean lawngrass (Zoysia japonica Steud.) as warm-season grass (WSG) and three blends and three mixtures of Kentucky bluegrass (KB, Poa pratensis L.), perennial ryegrass (PR, Lolium perenne L.), and tall fescue (TF, Festuca arundinacea Schreb.) as cool-season grass (CSG). Significant differences were observed in visual turf color and green color retention among soil systems and turfgrasses. Both the multi-layer and USGA systems were highly associated with better color ratings and longer color retention, as compared with the mono-layer system. Seasonal variation of visual turf color greatly occurred from late December to early spring. CSG exhibited longer color retention than did WSG. The latter maintained green color for approximately 6 months, regardless of the soil system. Spring green-up of Korean lawngrass occurred from early to middle May, while it underwent discoloration from late October to early November. Among the CSGs green-up occurred between early March and early April and leaf color was maintained until middle December to early February. Therefore, the CSGs were green for 8.5 to 11 months, depending on turfgrass and soil system. The mean period of green color duration across all soil systems was approximately 10-11, 9-10 and 8.5-9.0 months for PR, KB and TF, respectively. As for the CSG mixtures, the greater the proportion of PR, the longer the green color retention, while the higher the proportion of TF, the shorter the color retention. There was greater variation in green color duration among the CSGs than the WSGs. Across soil systems, color retention differences of 2 to 6 days were observed for the Korean lawngrass, but 7 to 36 days for the CSGs. These results demonstrate that green color retention varied greatly according to soil systems and also among turfgrasses. Selections of turfgrass and soil system should be made using a concept-oriented approach, when establishing garden, park, soccer field, golf course and other sports field. Information obtained in this study can be used to select soil systems and turfgrasses based on the expected degree of leaf color retention.

• Korean Journal of Environment and Ecology
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• v.18 no.4
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• pp.369-381
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• 2004

This study was achieved to present the way to restore the Seonheulgot pasture-grassland damaged by landuse and interference for a long time to evergreen broad-leaved forests as the native vegetation structure. As a result of analyzing ecological succession tendency of structure in survey area, we established the optimal restoration model. The total of survey sites were 26, and the classified plant community types were four types by M.I.P of dominant woody species. Finally we classified the four types based on diameter of dominant woody species in canopy layer. The six community types are as follows: Community I was runner-shrub forest, community II was evergreen broad-leaved shrub forest, and community III was evergreen broad-leaved forest of small diameter. Community IV and V were evergreen broad-leaved forest of middle diameter. Community Ⅵ was evergreen broad-leaved forest of large diameter. The number of constituent species was 24 in community I, 28 in community II as the shrub forest, 16 as the evergreen broad-leaved forest of small diameter, 29 in community III, 30 in community IV as the evergreen broad-leaved forest of middle diameter and 27 in community Ⅵ as the evergreen broad-leaved forest of large diameter. The range of Shannon's index of all communitys was from 0.8763 to 1.2630 and the Similarity index between the community composed of middle diameter woody species and large diameter woody species. The ecological succession of community I, II, and III were changed from pasture-grassland to broad-leaved forest and the structure of community IV, V, and Ⅵ was similar to evergreen broad-leaved forest in warm temperate region. We suggest the restoration planting model evergreen broad-leaved forest of in Seonheulgot pasture-grassland, as follows: The target restoration vegetation were Castanopsis cuspidata var. sievoldii community and Queycus glauca community. Castanopsis cuspidata var. sievoldii and Quercus glauca should be dominant woody species in canopy layer, the number of trees was 10 per 100$m^2$, and Castanopsis cuspidata var, sievoldii, Quercus glauca, Camellia japonica, and Eurya japonica should be dominant woody species in the understory layer, the number of trees was 14 per 100$m^2$.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.7
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• pp.1-8
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• 2019

The primary purposes of this study are to understand a fundamental effects of electro-deposition on reinforcing steel in saturated Ca(OH)2 electrolyte, and evaluate the corrosion rates of rebars under cyclic 3wt.%NaCl immersion and dry corrosion environment. The three cement mortar specimens with cover thickness 5, 10 and 30mm, were prepared in the experiment. To monitor the corrosion rates of rebars in mortar, the three cement mortar specimens were exposed to 110 wet-drying cycles(8-hour-immersion in 3wt.%NaCl and 16-hour-drying in a room temperature) in the laboratory. During the wet-dry cycles, the polarization resistance, Rp, and solution resistance, Rs, were continuously measured. The instantaneous corrosion rates of rebars on the effect of electro-depositing with sat. Ca(OH)2 electrolyte were estimated from obtained R-1p and degrees of wetness were estimated from Rs values. From the experimental results, the corrosion rates of rebars were greatly accelerated by wet/dry cycles. During the mortars exposed to drying condition, the large increases in the corrosion rates were showed at all rebar surfaces in three mortar specimen, attributed from the accelerated reduction rates of dissolved oxygen in drying process. However, the corrosion rates on rebar surface electrochemically deposited with sat. Ca(OH)2 electrolyte showed the clear decreases, caused by calcium deposits in the porous rust layer.

• Journal of Animal Environmental Science
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• v.14 no.3
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• pp.183-192
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• 2008

This study was carried out to investigate the temperature, water balance, evaporation and physicochemical properties during the composting with pig slurry at a scraper system. The pig slurry was composted on farm trial using continuous aeration with turning machine for 5 month. A compost facility of rectangular concrete bin with dimension of 53 m (length) ${\times}$ 4.6 m (width) ${\times}$ 2 m (height) was bedded with sawdust. The environmental parameters were monitored in period of 5 months. The results were as follows ; 1. During the composting period, the temperature was varied in the range $50{\sim}70^{\circ}C$. The temperature of compost pile was highest in middle layer and lowest in under layer. Temperature difference between middle and under area of compost pile was $5{\sim}20^{\circ}C$. 2. The water content of compost pile varied $50{\sim}68%$. In the period of 50% of water content of compost pile, the temperature of compost was $20{\sim}30^{\circ}C$ and was not successfully composted. 3. In this study, total evaporation was 90% during composting. The amount of slurry per $1m^3$ sawdust by this method was $3.16m^3$ without treatment of effluent output. 4. The chemical properties of produced compost was high, but suitable for plant growth. Concentration of T-N, T-C in the final compost were 1.62, 34%, respectively.