• Journal of Industrial Technology
• /
• v.29 no.A
• /
• pp.55-60
• /
• 2009

Stabilization treatment is one of processes for wastes and their components to reduce their toxicity and migration rates to surroundings. Inorganic binders such as calcium hydroxide, blast furnace slag and red mud were tested for their potential applicability to in-situ stabilization of heavy metal contaminated tailings in the abandoned metal mines. Columns(150mm dia. ${\times}$ 450mm length) filled with mixtures of inorganic binders and tailing from the Geumjang mine with various mixing ratios of binders to tailings, 5%, 7% and 9% were applied artificial rainfall tests for 28 days. Effluents from columns filled with calcium hydroxide and tailing showed high pH's of ~12.5 and a increasing trend of concentration in Pb and Zn with a significant decrease in permeability in terms of elapsed days. Those with burning slag and tailing showed pH's of ~8.5 and significantly low concentrations in heavy metals with a stable permeability. In case of red mud, effluents showed significantly low concentrations in heavy metals but a decreased permeability with pH's of ~10.5. Conclusively, this basic study suggests burning furnace slag be a potential stabilizer for effective treatment of heavy metal contaminated mine tailings.

• Journal of Korean Society of Forest Science
• /
• v.76 no.1
• /
• pp.11-16
• /
• 1987

With the purpose of pursuing the increase and decrease of chlorophyll a and chlorophyll b caused by application of the simulated acid rain treatment on Pinus koraiensis seedlings and Ligustrum obtusifolium cuttings, the experimental design of randomized block arrangement with three replications was implemented in the experimental field of Yesan National Agricultural Junior College, during the growing season of 1985. Pinus koraiensis seeds stratified in cool and moist condition were sown on pots, and in case of Ligustrum obtusifolium, C1/1 cuttings were potted for experimental use in the early spring. The regime of artificial acid rain, based upon precipitation frequency and density, was simulated from the learning of climatological data averaged from 30 years records. The spray of acid water containing pH values of 4.0 and 2.0 was initiated from the 1st of May and ended on the 31st of August. As control, ground water was also treated at the same time. To analyse the chlorophyll content, those leaves looking representative and unaffected by other harmful agents were sampled on the 18th of September, and UV-visible spectrophotometer was used. With decrease in pH values of acid rain, the content of chlorophyll a and chlorophyll b decreased in both species. The decrease in chlorophyll a could be confirmed through statistical significance, but not in chlorophyll b. And when we discussed the chlorophyll decrease index which was explained in detail in the paper, an attention might be given to similarly decreasing values in both chlorophyll a and chlorophyll b, according as pH levels of acid rain decreased. The ratios of chlorophyll a to chlorophyll b in both species were not affected by different pH leaves of acid rain.

• Corrosion Science and Technology
• /
• v.8 no.1
• /
• pp.40-43
• /
• 2009

We investigated the corrosion resistance of Zn and Cu coated steel pipes as a substitute for Cu pipe in an air-conditioner system. In addition, the galvanic corrosion tendency between two dissimilar metal parts was studied. The corrosion resistance of the Cu electroplated steel was similar to that of Cu, while the corrosion rate of the Zn electro- galvanized and the galvalume (Zn-55 % Al) coated steels was much higher and not suitable for Cu substitute in artificial sea water and acidic rain environments. Furthermore, the galvanic difference between Cu electroplated steel and Cu was so small that the Cu coated steel pipe can be used as a substitute for Cu pipe in an air-conditioner system.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2004.05b
• /
• pp.65-68
• /
• 2004

This paper researched leakage current characteristics of artificially contaminated EHV insulators through construction of long-term testing facility. Insulators were contaminated and classified into the ESDD contaminated levels under IEC standards method. As the test results of contaminated insulators was carried out several experiments, leakage current greatly increased during initial rainfall. After contaminated insulators were naturally washed by rain, leakage current was not increased.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2004.07b
• /
• pp.1166-1170
• /
• 2004

The leakage currents of transmission insulator were investigated as a function of environmental conditions, such as temperature, humidity, and rainfall. The insulators were artificially contaminated with insoluble yellow soil and kaolin which helped salt to stick on the surface of insulator. The insulators contaminated with the grade of B, C, and D were installed in the KoChang Testing Center. The leakage currents were measured and compared with non-contaminated insulators. The results indicated that the most important factor affecting leakage current was humidity. After heavy rain, the artificially contaminated salt was dissolved, resulting in similar characteristics between with and without contamination

• Magazine of the Korea Concrete Institute
• /
• v.8 no.1
• /
• pp.138-144
• /
• 1996

At present, waterproof is absolutely needed to minimize the carbonation of bridge decks in Kor ea. In this research indoor experiments for penetrative waterproof admixture out of available methods are carried out to evaluate the resisting characteristics against natural arid artificial car bona ting conditions. The test results show that the optimal time of waterproof is 14 days after the concrete construc. tion but reconsideration is necessary for the application to high strength concrete because of the reduction in penetration of waterproof admixture. The results also show that the penetrat ive waterproof admixture has srrong resistance to the acid rain. However the waterproof capability of the admixture is not permanent especially under the natural exposure. Therefore the slab of a bridge should be paved with asphalt concrete. Other noticeable effects are the increase of heat and abrasion resistances from the use of the waterproof agents.

• Wind and Structures
• /
• v.26 no.4
• /
• pp.215-229
• /
• 2018

The appearance of a rivulet at the upper surface of a stay cable is responsible for rain-wind-induced vibration (RWIV) of cables of cable-stayed bridges. However, the formation mechanism of the upper rivulet and its aerodynamic effects on the stay cable has not been fully understood. Large eddy simulation (LES) method is used to investigate flow around and aerodynamics of a circular cylinder with an upper rivulet at a Reynolds number of 140,000. Results show that the mean lift coefficients of the circular cylinder experience three distinct stages, zero-lift stage, positive-lift stage and negative-lift stage as the rivulet located at various positions. Both pressure-induced and friction-induced aerodynamic forces on the upper rivulet are helpful for its appearance on the upside of the stay cable. The friction-induced aerodynamic forces, which have not been considered in the previous theoretical models, may not be neglected in modeling the RWIV. In positive-lift stage, the shear layer separated from the upper rivulet can reattach on the surface of the cylinder and form separation bubbles, which result in a high non-zero mean lift of the cylinder and potentially induces the occurrence of RWIV. The separation bubbles are intrinsically unsteady flow phenomena. A serial of small eddies first appears in the laminar shear layer separated from the upper rivulet, which then coalesces and reattaches on the side surface of the cylinder and eventually sheds into the wake.

• Korean journal of applied entomology
• /
• v.19 no.1 s.42
• /
• pp.39-44
• /
• 1980

The outbreak of the pear rust caused by Gymnosporangium haraenum SYDOW has increased gradually since 1973, and amounted to 60.3 percent infection of leaves in 1975. But it has reduced due to regulation of juniper plantings by Plant Protection Law enacted in 1974. The teliospores of C. haraeanum germinated from middle of April to middle of May under natural condition. The germination of teliospores was observed 5 day earlier under laboratory condition with the artificial rainfall than that of natural condition. It was required considerable rainfall and longer than 3hr rainy period to germinate teliospores after being matured. Infection of rear leaves took place in the rain or just after the rain, but not after 24hr. The incubation period of G. haraeanum on the leaf was 9 to 10 days. In case that the distance between orchard and juniper trees was less than loom, almost all of the pears were infected, but the chance oft infection reduced in proportion as the distance increased. No infection occurred at the distance of further than 2000m.

• Journal of Environmental Science International
• /
• v.19 no.2
• /
• pp.229-236
• /
• 2010

As air pollution has emerged as one of the most pressing urban environmental concerns, many studies have investigated the influence of air pollutants(ex: $O^3$, $NO^2$, $SO^2$, Acid rain, etc.) on roadside trees and urban grove. In Korea, population density started to increase since the industrialization. Since dense population aggravates our living conditions, it's very important for us to preserve and keep a lively and refreshing nature in order to live with green nature in harmony under the current artificial environment-dominating world. In metropolitan cities, the production of pollutants increases in proportion to population growth. The vehicle exhaust gas and air pollutants from cooling and heating systems have been the major causes of acid rain. Furthermore, tire particles which are naturally produced by tire wearing on roads and other toxic substances in exhaust gas have caused a problem in human health directly and indirectly. In fact, a lot of studies have analyzed air pollution, roadside trees and plants in Korea. However, they are mostly limited to covering the influence of air pollution on the growth of plants. No paper has clearly explained why air pollution-resistant or-vulnerable species has shown different reactions yet. Even though a lot of urban roadside trees have died or stopped to grow from time to time, this kind of problem has not been properly examined. This paper is aimed to comparatively analyze physio-ecological characteristic such as photosynthesis, chlorophyll contents, soil volume water figure out their relationship with environmental factors against the expanding roadside trees in Cheong-ju, and provide basic data for management of roadside trees and elaboration of urban environment preservation policies.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2023.05a
• /
• pp.168-168
• /
• 2023

The frequent occurrence of cyanobacterial harmful algal blooms (CHABs) in inland waters under climate change seriously damages the ecosystem and human health and is becoming a big problem in South Korea. Satellite remote sensing is suggested for effective monitoring CHABs at a larger scale of water bodies since the traditional method based on sparse in-situ networks is limited in space. However, utilizing a standalone variable of satellite reflectances in common CHABs dual-models, which relies on both chlorophyll-a (Chl-a) and phycocyanin or cyanobacteria cells (Cyano-cell), is not fully beneficial because their seasonal variation is highly impacted by surrounding meteorological and bio-environmental factors. Along with the development of Artificial Intelligence (AI), monitoring CHABs from space with analyzing the effects of environmental factors is accessible. This study aimed to investigate the potential application of AI in the dual-model strategy (Chl-a and Cyano-cell are output parameters) for monitoring seasonal dynamics of CHABs from satellites over Korean inland waters. The Sentinel-3 satellite was selected in this study due to the variety of spectral bands and its unique band (620 nm), which is sensitive to cyanobacteria. Via the AI-based feature selection, we analyzed the relationships between two output parameters and major parameters (satellite water-leaving reflectances at different spectral bands), together with auxiliary (meteorological and bio-environmental) parameters, to select the most important ones. Several AI models were then employed for modelling Chl-a and Cyano-cell concentration from those selected important parameters. Performance evaluation of the AI models and their comparison to traditional semi-analytical models were conducted to demonstrate whether AI models (using water-leaving reflectances and environmental variables) outperform traditional models (using water-leaving reflectances only) and which AI models are superior for monitoring CHABs from Sentinel-3 satellite over a Korean inland water body.