• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.4
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• pp.304-311
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• 2006

Experiments on evaporative spray cooling on the square plate heaters with plain or micro-porous coated surfaces were performed in this study. Micro-porous coated surfaces were made by using DOM [Diamond particle, Omegabond 101, Methyl-Ethyl-Keton] method. In case of purely air-jet cooling, the micro-porous coating doesn't affect the cooling capacity. In spray cooling three different flow patterns (complete wetting, evaporative wetting, dryout) are observed on both plain and micro-porous coated surfaces. The effects of various operating conditions, such as water flow rate, particle size, and coating thickness were investigated on the micro-porous coated surfaces. It is found that the level of surface wetting is an important factor to determine the performance of spray cooling. It depends on the balance between absorbed liquid amount by capillary force over porosity and the evaporative amount. The micro-porous coated surface has largest cooling capacity, especially in the evaporative wetting zone. It is found that the effects of liquid flow rate and coating thickness are significant in evaporative wetting zone, but are not in complete wetting and dryout zones.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.63 no.3
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• pp.186-195
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• 2018

A field study was conducted over a 3-year period from 2014 to 2016 in the central plain area, Suwon, Korea, 1) to compare the biomass production between machine-transplanted and water-broadcast seeded silage rice and 2) to elucidate the growth factors that affect the difference in biomass production between the two cultivation practices. The heading date for the water-broadcast seeded silage rice was September 11-18, which was delayed by 11-17 days when compared to that for the machine-transplanted silage rice. On average, water-broadcast seeded silage rice had a shorter plant height, more panicles per area, and a greater biomass production because of the increased straw dry weight. However, the difference in dry weight of each plant organ between the two cultivation practices exhibited yearly variation. When the data were pooled across experimental years, cultivation practices, and varieties, biomass production was highly positively correlated with straw dry weight but not with panicle dry weight. When the ratio of water-broadcast seeding to machine-transplanting was analyzed, total dry weight and straw dry weight were positively associated with each other, whereas no relationship was found between total dry weight and panicle dry weight. Despite that water-broadcast seeded silage rice produced more panicles per area than machine-transplanted silage rice, the two cultivation practices had a similar dry weight per culm. Therefore, we conclude that the silage rice from the water-broadcast seeding, compared to the machine-transplanting, produced more biomass because of the combination of the increased panicle number per area and a similar dry weight per culm. These results suggest that silage rice could be produced through water-broadcast seeding to increase biomass production with low labor and cost input.

• Journal of the Korea Institute of Building Construction
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• v.17 no.3
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• pp.227-234
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• 2017

This research analyzes the properties of mortar following the rise in water-cement ratio and applicability as an eco-friendly construction supply by using the mudflats of a dredged arena as a substitute for aggregate. The results of a experiment of the flow showed that the flow value decreases as the amount of mudflats increases. A test for chloride content showed that the chloride content increases with the amount of mudflats. In the compression of specimen mixed with mudflat and the testing of tensile strength, the strength weakened as the addition ratio of mudflats rose. However, with 14-day strength as the standard, most specimen showed more strength than the plain, and 14-day strength was higher than 28-day strength. It appears to be experimental error in the mixing process from the viscosity and cohesion of mudflats, and it is considered that there will be a need for an experiment on mixing methods of mudflats in the future. The compressive strength of this research was the strongest with 70% in water-cement ratio, and the tensile strength was strongest with 80% in water-cement ratio. In the evaluation of surface analysis, 70% water-cement ratio, which is finest in strength, mixing, and compactness, was selected to analyze the roughness of the surface, and the results showed that the surface became smoother as the addition ratio of mudflats increases. In conclusion, it appears that 70% water-cement ratio is the optimal mixing ratio for mortar and 10 to 30% addition ratio of mudflats the optimal ratio. It also appears that the application of interior finishing material like bricks and tiles and interior plastering material using the mudflats are possible.

• Korean Journal of Plant Resources
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• v.19 no.6
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• pp.687-691
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• 2006

This experiment was conducted on rice (cv. 2005 Thaoi) seeds to study whether priming with deep sea water (DSW) results in enhancement of seed emergence and seedling growth and to identify the optimum concentration of Deep Sea Water (DSW) for priming. Two experiments were conducted subsequently. In experiment 1, four concentrations of the DSW (10%, 20%, 30% and 40%), and in experiment 2, five concentrations of DSW (10%, 15%, 20%, 25% and 30%) were prepared and seeds were primed for 24 hours duration at $25^{\circ}C$. Beside this, hydro priming with plain water was also included as a control. Experiments were laid out in Completely Randomized Design (CRD) with three replications. Result showed that 20% DSW seed priming treatment had improved the emergence, seedling height, number of roots and root length as compare to other with DSW or without DSW treatments. Beyond 20% DSW priming (i.e. 25%, 30% and 40%) were not suitable for priming the seed. On the basis of seedlings growth parameters; emergence, seedling height, root number and length, and shoot root ratio, 20% DSW priming was the best priming treatment.

• Structural Engineering and Mechanics
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• v.22 no.1
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• pp.71-83
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• 2006

This paper deals with the effects of various moisture environments on the structural behavior of concrete beams. The presented results were obtained within a large experimental program carried out at the Laboratoire Central des Ponts et Chauss$\acute{e}$es (LCPC), with Electricit$\acute{e}$ de France (EDF) as a partner. The aim of this paper is to point out and to quantify the strains resulting from unidirectional moisture conditions: a drying gradient applied during 14 months, followed by the re-wetting of the dried surface during 9 months. The effect of reinforcement on the shrinkage and on the deformation due to water absorption is pointed out. Moreover, a lot of tests on companion cylinders and prisms were carried out to determine the mechanical characteristics of the material and help checking analysis methods. The paper focuses on numerous measurements obtained during the 23 months on one plain concrete beam and one reinforced concrete beam: variation of water content, followed by precise weighing and gammadensitometry, relative humidity measurements, local and global deformations in the three directions and deflection of the beams. Thus, the effects of drying and water absorption on the behavior of concrete structures are documented and analyzed in comparison with existing representation of water diffusion.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.8 no.4
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• pp.1-11
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• 2005

Yangjae stream was divided with Seoul and Gwacheon reach. Seoul reach was ecologically restored; however, Gwacheon reach was not. Similarity index of the bird communities between the two areas was relatively high, 79.9%. The dominant species in Seoul reach were Passer montanus, Pica pica, Paradoxornis webbianus and Anas crecca. The dominant species in Gwacheon reach were Passer montanus, Pica pica, Paradoxornis webbianus and Streptopelia orientalis. The different species was Anas crecca in Seoul and Streptopelia orientalis in Gwacheon. An eco-park was constructed along the stream of Seoul reach since 1996 but was not in Gwacheon reach; the number of species has increased in Seoul area($r^2$=0.846, p<0.01), but Gwacheon was not change($r^2$=0.023, p>0.05) since 1996. The number of individuals, however, was almost constant in both reaches(Seoul : $r^2$=0.211, p>0.05, Gwacheon : $r^2$=0.032, p>0.05). In Seoul reach, the ecological restoration of stream was helpful to increase bird diversity. The number of waterbirds such as herons, plovers, sandpipers and wagtails was higher in Gwacheon reach than in Seoul reach, but the number of ducks and songbirds was higher in Seoul reach than in Gwacheon reach. We suggest that the ecological restoration in Seoul area might have negative effects on sandpipers, plovers and wagtails inhabiting on the flood plain in stream, but positive effects on other species such as herons, ducks and songbirds. Especially, the increasing number of ducks was attributed to an artificial pond in flood plain. The difference in the number of Streptopelia orientalis between both reaches was owing to the habitat differences such as forest trees playing a role as patch in high revetment. From the present investigation, it could be concluded that the ecological restoration of the local stream must be carried out with consideration of water channels, sand banks and water front in addition to the high revetment for birds to attract diverse bird communities.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1571-1575
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• 2006

Channel form discharge which determines shape and character of a channel is named as dominant discharge. Assuming that fixed discharge flows in the fluvial plain for a long time, it is channel form discharge of a certain channel if it changes the fluvial plain into shape of the channel. Channel form discharge can be demonstrated by concept of bankfull or effective discharge. 1.01, 1.58, 2, 2.33 and 5 year flood discharge were used in order to determine channel form discharge. Each frequency discharge was determined by 80 year flood discharge by a research result conducted by Kim and Won. 1.01 year frequency discharge was selected as the most similar discharge to bankfull discharge. 1.58 year frequency discharge habitually used in Korea exceeded bankfull discharge.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1107-1111
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• 2006

Channel form discharge which determines shape and character of a channel is named as dominant discharge. Assuming that fixed discharge flows in the fluvial plain for a long time, it is channel form discharge of a certain channel if it changes the fluvial plain into shape of the channel. Channel form discharge can be demonstrated by concept of bankfull or effective discharge. 1.01, 1.58, 2, 2.33 and 5 year flood discharge were used in order to determine channel form discharge. Each frequency discharge was determined by 80 year flood discharge by a research result conducted by Kim and Won. 1.01 year frequency discharge was selected as the most similar discharge to bankfull discharge. 1.58 year frequency discharge habitually used in Korea exceeded bankfull discharge.

• Magazine of the Korea Concrete Institute
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• v.6 no.1
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• pp.142-151
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• 1994

The purpose of this study is to investigate anti analyze the effect of iength of steel fiber and concrete admixt.ure such as iilica fume and fly ash on the workability arid engineering properties cbf steel fiber reinforced concxte (SFRC). As the results the follows art: found. First, it is poss ible to make steel fiber reinforced concrete having the consistency of IOcm slump and 28 days compressive strength of $600{\;}kgf/\textrm{m}^2$ by adopting low water binder ratios arid using :uperplasticizer. Second, the conipresslve and tensile strength of SWKC containing silica fume and fly ash is lower than those of plain concrete in the age after 28 days, but higher in the age after 28 days. Finally, tensde strength of SFHC is higher than that of plain concrete, and so adding the steel fibers in concrete increases the toughness.

• The Journal of the Korea Contents Association
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• v.9 no.10
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• pp.417-426
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• 2009

The eco-friendly river restoration issue has been increased and the importance of the vegetation along the river banks has been understood with its scenery and significant role. However vegetation reduces the stream flow cross section and brings negative effects such as increase of water flow resistance and decreases of river flow velocity. In this study, the method to choose roughness coefficient is studied in the sudden changed hydraulic characteristics by river restoration. Using the HEC-RAS model and the two-dimensional vertical analysis method, Yangjae stream was calculated that the roughness coefficient of the main channel is 0.011~0.159 after river restoration, 0.031 without vegetation on the flood plain, and 0.034~0.506 with vegetation on the flood plain. The level of water in the river is predicted to rise 0.13~0.34m at 30% of vegetation density increase.