• Journal of the Korean Society of Environmental Restoration Technology
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• v.6 no.4
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• pp.62-73
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• 2003

The study was to apply a mat style reed planting method at confluence to improve plants growth conditions by relaxing disturbed topographical base due to water flow and was intended to review the effect to build up a vegetation strip by monitoring process after the construction. First off, We've attempted to construct reed mats on selected sites as confluences of Tan and Gaehwa stream and then examined and analyzed characteristics of soil and vegetation community. As the results of the examination, the soil texture was proven to be a mix of sand and loamy sand and be 6.3 ~ 7.0 soil pH. In addition, it contained 1.0 ~ 4.6% of organic matter, 0.04 ~ 0.22% of T-N and 27.8 ~ 41.2% of water content. For its vegetation structure, the Tan stream confluence was first actually a point bar without plants prior to the construction but 8 kinds of hygrophytes including Persicaria hydropiper and 9 kinds of terrestrial plants such as Potentilla supina, Artemisia annua, and Alopecurus aequalis var. amurensis. On the other hand, the Gaehwa stream confluence contained 6 kinds of hygrophytes such as Bidens frondosa and other 11 kinds of terrestrial plants prior to the construction while it produced 7 kinds of hygrophytes including Ranunculus ternatus as well as Phragmites australis and 9 kinds of terrestrial plants such as Potentilla supina after the construction. For the Phragmites australis, almost of them was weathered away in early days just after planting because of development period passed, but on May, six months later from planting, it was investigated that its length was approximated as 65 ~ 85cm with 75% coverage and that the number of it was 437 ~ 633/$m^2$. The study was shown that reed mats can improve environmental conditions of disturbed topographical base, enabling natural growth of various riparian vegetation including the introduced plant, reed. In the meantime, it was supposedly judged that to recover or build up a vegetarian strip, supplementary materials should be prepared to help produce and grow plants because it is not probable to expect river drift by water flow at confluence and that corrosion, burying or inundation owing to changes of water lever should be considered.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.5 no.1
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• pp.10-17
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• 1993

This paper describes the boiling heat transfer phenomena to be divided into three regions, nonboiling, nucleate boiling and burn-out in the impinging subcooled water jet system. In the nonboiling region, Nusselt number is a function of Prandtl number, Reynolds number and ${\Delta}T_{sub}/T_{ast}$ In the nucleate boiling region, the heat flux increases with increment of the nozzle exit velocity. But the degree of liquid subcooling does not affect the shape of the nucleate boilng curve. The dimensionless correlations can be expressed in the form of $q{\ell}/K_f{\Delta}T_{ast}=C(Bo{\cdot}C_p{\cdot}{\Delta}T_{sat}/Vo^2)^m{\cdot}(Re/We)^n$. The burn-out heat flux increases linearly with increment of the nozzle exit velocity, but independs of degree of subcooling and the supplementary water height.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.974-981
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• 2007

Seoul Metro has operated the air cooling equipment established in a machine room of a station building to improve our services focused on our customers who use Seoul Metro during the summer season. However, a new set of problems has arisen with the cooling tower to support a heat exchange of cooling water. One of them is loss of efficiency in the air conditioner. The leading cause of this problem is that we use an underground type of the cooling tower. As the machine room of a station building is located in the underground of inner city because of the nature of the subway, it is difficult to establish the cooling tower on the ground. The underground structure of the No. $1{\sim}4$ subway line is unsuitable for the location requirements of the underground type of the one because it has a limited space to set up the air cooling equipment, for example, the cooling tower and a ventilating opening. As a result of such an unfavorable condition, the cooling tower doesn't work efficiently and the warmth of cooling water because of insufficiency of a heat exchange and a refrigerator's technical obstacle such as a high-temperature and a high-pressure has arisen. Accordingly, the efficiency of the air conditioning is getting lower and lower. Another problem is too wasteful with water. Each station uses the water over 30 tons every day with waterworks to replenish the cooling tower such as a evaporation, a scattering and a distribution of water. Nevertheless, the more an air conditioner increase, the more the use of water supply increase. For this reason, we can't help wasting an enormous amount of water and discharging the congelation of a low temperature(about $15^{\circ}C$) occurred in a heat exchanger inside an air conditioner. The purpose of this study is to analyze the utility of congealing water to improve efficiency of the air cooling equipment and save energy as a supplementary water for the cooling tower.

• Journal of Korean Society on Water Environment
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• v.30 no.6
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• pp.585-595
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• 2014

The temporal trends of the prioritized toxic water pollutants generated and discharged from the industrial facilities in the Geum-River basin, Korea were analyzed with the results of the nationwide Water Pollution Source Survey conducted in 2001 - 2012. The statistical results indicated rapid increase in the volume of raw toxic wastewaters whereas the amount of each toxic pollutant kept fluctuating for 12 years. Serious discrepancies in the survey data of the same type of industries demonstrated a low reliability of the survey result, which stemmed from several error factors. A unit-load for each type of industrial facility was devised to estimate the amount of prioritized toxic water pollutant based on the total volume of industrial wastewater generated from the same type of industrial facilities. The supplementary measures with an effective permit issuance policy and adding survey parameters of terminal wastewater treatment plants to use them as references to the Water Pollution Source Survey were suggested as means to minimize the errors associated with the false reports from the industries.

• Corrosion Science and Technology
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• v.6 no.3
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• pp.90-95
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• 2007

Cathodic protection technology has been widely used on ship's outer hull and inner side of ballast water tanks as a supplementary corrosion protection measure in combination with protective organic coatings. Impressed current cathodic protection system is typically opted for the ship's hull and, sacrificial anode system, for ballast water tanks. The anticipation and interest in cathodic protection system for ships has been surprisingly low-eyed to date in comparison with protective coatings. Computational analysis for the verification of cathodic protection design has been tried sometimes for offshore marine structures, however, in commercial shipbuilding section, decades old design practice is still applied, and no systematic or analytical verification work has been done for that. In this respect, over-rotection from un-erified initial design protocol has been also concerned by several experts. Especially, it was frequently reported in sacrificial anode system that even after full design life time, anode was remaining nearly intact. Another issue for impressed current system, for example, is that the anode shield area design for ship's outer hull should be compromised with actual application situation, because the state-of-the-art design equation is quite impractical from the applicator's stand. Besides that, in this study, some other critical design issues for sacrificial anode and impressed current cathodic protection system were discussed.

• Advances in concrete construction
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• v.8 no.2
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• pp.119-126
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• 2019

This paper reports an experimental investigation conducted to evaluate the durability performance of concrete mixtures prepared utilizing blends of Type I Portland cement (OPC) and natural pozzolans (NPs) obtained from three different sources in Saudi Arabia. The control concrete mixture containing OPC alone as the binder and three concrete mixtures incorporating NPs were prepared keeping water/binder ratio of 0.4 (by weight), binder content of $370kg/m^3$, and fine/total aggregate ratio of 0.38 (by weight) invariant. The compressive strength and durability properties that included depth of water penetration, depth of carbonation, chloride diffusion coefficient, and resistance to reinforcement corrosion and sulfate attack were determined. Results of this study indicate that at all ages, the compressive strength of NP-admixed concrete mixtures was slightly less than that of the concrete containing OPC alone. However, the concrete mixtures containing NP exhibited lower depth of water penetration and chloride diffusion coefficient and more resistance to reinforcement corrosion and sulfate attack as compared to OPC. NP-admixed concrete showed relatively more depth of carbonation than OPC when subjected to accelerated carbonation. The results of this investigation indicates the viability of utilizing of Saudi natural pozzolans for improving the durability characteristics of concrete subjected to chloride and sulfate exposures.

• Advances in concrete construction
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• v.3 no.1
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• pp.71-90
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• 2015

In order to investigate the feasibility and advantage of tuff used as pozzolan in cement-based composite, the representative specimens of tuff were collected, and their chemical compositions, proportion of vitreous phase, mineral species, and rock structure were measured by chemical composition analysis, petrographic analysis, and XRD. Pozzolanic activity strength index of tuff was tested by the ratio of the compression strength of the tuff/cement mortar to that of a control cement mortar. Pozzolanic reaction degree, and the contents of CH and bond water in the tuff/cement paste were determined by selective hydrochloric acid dissolution, and DSC-TG, respectively. The tuffs were demonstrated to be qualified supplementary binding material in cement-based composite according to relevant standards. The tuffs possessed abundant $SiO_2+Al_2O_3$ on chemical composition and plentiful content of amorphous phase on rock texture. The pozzolanic reaction degrees of the tuffs in the tuff/cement pastes were gradually increased with prolongation of curing time. The consistency of CH consumption and pozzolanic reaction degree was revealed. Variation of the pozzolanic reaction degree was enhanced with the bond water content and relationship between them appeared to satisfy an approximating linear law. The fitting linear regression equation can be applied to mutual conversion between pozzolanic reaction degree and bond water content.

• Proceedings of the Korean Society of Crop Science Conference
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• 2001.09a
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• pp.59-71
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• 2001

In Korea, It was natural and inevitable to reclaim tidal land for farming due to over-population in small territory. Looking back upon the history of tidal land reclamation in Korea, We can find the first case of it in 13th century KangHwaDo(Island), and also find several records of small scale reclamations of western sea-coast from Korea dynasty to Chosun dynasty. A lot of wide fertile agricultural areas on western sea-coast have been developed through tidal land reclamation for about 1000-year after Korea dynasty. and on these areas, we have produced rice which we live on. An average areas of farming land per capital in korea is only 0.04ha, which is one sixth of global average. For water resources, similarly, capacity of water resources alloted to one person is $11{\%}$ of global average. So, without supplementary water development, we will have suffered from a severe deficiency of water Therefore we must prepare for these predictable short water and food problems. and tidal land reclamation may be suitable alternative to settle these problems. However, tidal land reclamation is a work of closing estuary, intercepting sea water inflow, developing a freshened estuary lake and farming lands etc. therefore it apparently causes a change of ecosystem, water quality and littoral environment. Nowadays, widely recognized the importance of environmental preservation, it is desirable or requested to make phil-environmental and sustainable development minimizing the environmental influence due to tidal land reclamation project. In this paper, the role of tidal land reclamation project in the development process of Korean agriculture was reviewed and the direction of afterwards tidal land reclamation project was suggested.

• Journal of The Korean Society of Agricultural Engineers
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• v.66 no.3
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• pp.25-37
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• 2024

Global warming-induced drought inflicts significant socio-economic and environmental damage. In Korea, the persistent drought in the southern region since 2022 has severely affected water supplies, agriculture, forests, and ecosystems due to uneven precipitation distribution. To effectively prepare for and mitigate such impacts, it is imperative to develop proactive measures supported by early monitoring systems. In this study, we analyzed the spatiotemporal changes of multiple evapotranspiration-based drought indices, focusing on the flash drought event in the southern region in 2022. The indices included the Evaporative Demand Drought Index (EDDI), Standardized Precipitation Evapotranspiration Index (SPEI) considering precipitation and temperature, and the Evaporative Stress Index (ESI) based on satellite images. The Standardized Precipitation Index (SPI) and SPEI indices utilized temperature and precipitation data from meteorological observation stations, while the ESI index was based on satellite image data provided by the MODIS sensor on the Terra satellite. Additionally, we utilized the Evaporative Demand Drought Index (EDDI) provided by the North Oceanic and Atmospheric Administration (NOAA) as a supplementary index to ESI, enabling us to perform more effective drought monitoring. We compared the degree and extent of drought in the southern region through four drought indices, and analyzed the causes and effects of drought from various perspectives. Findings indicate that the ESI is more sensitive in detecting the timing and scope of drought, aligning closely with observed drought trends.

• Asian-Australasian Journal of Animal Sciences
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• v.30 no.12
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• pp.1773-1783
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• 2017

Objective: This study evaluated the supplementary effect of higher concentrations of various disaccharides on processing yield, major physicochemical properties, and sensory attributes of Chinese-style pork jerky (CSPJ). Methods: CSPJ samples were prepared by marinating sliced ham (4 mm) with three dissaccharides, including sucrose, lactose, and maltose, at 0%, 15%, 18%, 21%, and 24%. Subsequently, the CSPJ samples were dried and roasted. The moisture content, water activity, crude protein, moisture-to-protein ratio, pH, processing yield, shear force, color, and sensory attributes of the CSPJ samples were evaluated. Results: The quality characteristics of CSPJ samples prepared with sucrose were more acceptable. By contrast, CSPJ samples prepared with lactose showed the lowest scores. However, the processing yield and moisture content were the highest for CSPJ samples prepared with lactose, which may be associated with improved benefits for cost reduction. Furthermore, sucrose and lactose supplementation resulted in contrasting quality characteristics; for example, CSPJ samples with sucrose and maltose supplementation had higher sensory scores for color than samples with lactose supplementation. Additionally, most quality characteristics of CSPJ samples with sucrose supplementation contrasted with those of the samples with lactose supplementation; for example, the samples with sucrose supplementation had higher scores for sensory attributes than those with lactose supplementation. Conclusion: Sucrose supplementation up to 21% to 24% was associated with the highest overall acceptability scores (5.19 to 5.80), enhanced quality characteristics, increased processing yield, and reduced production cost.