• FLOWER RESEARCH JOURNAL
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• v.16 no.1
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• pp.63-70
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• 2008

This experiment was conducted to acquire the basic data necessary for the artificial pond greening. Eighty four hydrophytes collected from 11 domestic small ponds and a farm were used in this experiment. The size of the artificial pond used was $6m{\times}3m{\times}1.5m(length{\times}width{\times}depth)$. Twelve months after planting, species were selected for their high ornamental values and tissue contents of N and P in each month. Tissue contents of N in Trapha nantan, Nymphoides indica, Nymphaea hybrid, and Murdannia keisak were high. Tissue contents of P in Monochoria vaginalis and Murdannia keisak were also high. The pH of artificial pond stabilized at a 6.8~7.6 range from May 2005 to March 2007. The EC was low in summer and high in autumn. From April to October, 5, 19, 23, 32, 31, 28, and 26 species, respectively, were selected for artificial pond greening. One year after planting, vegetation changed from 78 species (Potamogeton octqandrus, Salvinia natans, Potamogeton malaianus, etc.) to 38 species (Scirpus tarbernaemontani, Scirpus karuizawensis, Scirpus triqueter, etc.). Species diversity in the artificial pond was as follows, indicating it being a stabilized artificial pond; 38 species, 1,437 total number of plants, species richness index of 11.72, and maximum diversity index of 0.97.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.3
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• pp.236-245
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• 2021

It is very important for structure designer to understand the service life variation since a wide range of service life is evaluated with changing exposure conditions and design parameters. Recently, for zero-carbon, waste plastic has been used for fuel for clinker production and this yields increase in chloride content in cement. This study is for evaluation of changing service life in the concrete with increasing initial chloride content due to usage of plastic-SRF(Solid Refuse Fuel) considering various exposure conditions and design parameters. For this, 4 levels of initial chloride content were assumed, and the service life was assessed using LIFE 365 program considering various environmental conditions including 3 levels of surface chloride content. As for analysis parameters, critical/initial chloride content, blast furnace slag powder replacement ratio, W/B(Water to Binder) ratio, cover depth, and unit mass for binder are adopted. Service life decreases with increasing initial chloride content and a significant reduction of service life is not evaluated permitting up to 1,000ppm of initial chloride content. With increasing slag replacement ratio, a longer service life can be secured since blast furnace slag powder has the effect of reducing the diffusion of external chloride ions and fixing the free chloride. It is thought that increasing initial chloride content up to European standard is helpful for enhancing sustainability and reducing carbon emission. Though the reduction in service life due to an increase in the initial chloride content is not significant in slag-concrete with low surface chloride content, careful consideration for mixing design should be paid for the exposure environment with high surface chloride content.

• The Journal of the Acoustical Society of Korea
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• v.38 no.4
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• pp.378-386
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• 2019

Unlike ship noise that radiates from moving ships, wind noise is caused by breaking waves as a result of the interaction between the wind and the sea surface. In this paper, WNL (Wind Noise Level) was modeled by considering the noise source of the wind as the bubble cloud generated by the breaking waves. In the modeling, SL( Source Level) of the wind noise was calculated using the wind-speed data measured from the weather buoy operated in the coastal area of the East Sea. At the same time as observing the wind speed, NL (Noise Level) was continuously measured using a self-recording hydrophone deployed near the weather buoy. The modeled WNL according to the wind speed and the measured NL removing the shipping noise from the acoustic raw data were compared in the low-frequency band. The overall trends between the modeled WNL and the measured NL were similar to each other. Therefore, it was confirmed that it is possible to model the WNL in the shallow water considering the SL and distribution depth of bubble cloud caused by the wind.

• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.2
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• pp.153-170
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• 2022

Waterjet has been comprehensively used in urban areas owing to a suitable technique for cutting concrete and rock, and low noise and vibration. Recently, the abrasive waterjet technique has been adopted and applied by the Korea Atomic Energy Research Institute to demolish concrete plugging without disturbing and damaging In-situ Demonstration of Engineered Barrier System in the disposal research tunnel. In this study, the use of abrasive waterjet in the tunnel was evaluated for practical applicability and the existing cutting model was compared with the experimental results. As a variable for waterjet cutting, multi-cutting, water flow rate, abrasive flow rate, and standoff distance were selected for the diversity of analysis. As regarding the practical application, the waterjet facilitated path selection for cutting the concrete plugging and prevented additional disturbances in the periphery. The pump's noise at idling was 64.9 dB which is satisfied with the noise regulatory standard, but it exceeded the standard at ejection to air and target concrete because the experiment was performed in the tunnel space. The experimental result showed that the error between the predicted and measured cutting volume was 12~13% for the first cut and 16% for second cut. The standoff distance had a significant influence on the cutting depth and width, and the error tended to decrease with decrement of standoff distance.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.25 no.2
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• pp.23-38
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• 2022

This study investigates the characteristics and physical habitat requirements for each Bufo gargarizans life history through a literature survey. After deriving variables for each component of Bufo gargarizans, in order to reduce regional deviations from eight previously studied literature research areas for deriving the criteria for variables, a total of 12 natural habitats of Bufo gargarizanss are selected as spatial ranges by selecting four additional sites such as Umyeonsan Ecological Park in Seoul, Wonheungibangjuk in Cheongju in the central region, Changnyeong Isan Reservoir in the southern region, and Mangwonji in Daegu. This study presents Bufo gargarizans SI, a species endemic to Korea, whose population is rapidly declining due to large-scale housing site development and road development, and develops a Bufo gargarizans HSI model accordingly to improve the function of the damaged Bufo gargarizans habitat and to present an objective basis for site selection of alternative habitat. At the same time, it provides basic data for adaptive management and follow-up monitoring. The three basic habitat requirements of amphibians, the physical habitat requirements of Bufo gargarizans, synthesized with shelter, food, and water, and the characteristics of each life history, are classified into five components by adding space and threats through literature research and expert advice. Variables are proposed by synthesizing and comparing the general characteristics of amphibians, among the previously studied single species of amphibians, the components of HSI of goldfrogs and Bufo gargarizans, and the ecological and physical environmental characteristics of Bufo gargarizans. Afterwards, through consultation with an amphibian expert, a total of 10 variables are finally presented by adjacent forest area(ha), the distance between spawning area and the nearest forest land(m), the soil, the distance from the wetland(m), the forest layered structure, the low grassland space, the permanent wetland area(ha), shoreline slope(%), PH, presence of predators, distance from road(m), presence or absence of obstacles. n order to derive the final criteria for each of the 10 variables, the criteria(alternative) for each variable are presented through geographic information analysis of the site survey area and field surveys of the previously studied literature research area. After a focus group interview(FGI) of 30 people related to the Bufo gargarizans colony in Cheongju, a questionnaire and in-depth interviews with three amphibians experts are conducted to verify and supplement the criteria for each final variable. Based on the finally developed Bufo gargarizans HSI, the Bufo gargarizans habitat model is presented through the SI graph model and the drawing centering on the Bufo gargarizans spawning area

• Composites Research
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• v.36 no.1
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• pp.37-41
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• 2023

The treated water inside the ballast electrolytic cell creates a highly alkaline atmosphere due to hydroxide generated at the DSA(Dimension Stable Anode) electrode during electrolysis. In this study, a composite material that can replace the weakness of the PE-coated steel pipe used in the existing ballast pipe was prepared. The test samples are BRE(Basalt fiber reinforced epoxy), BRP(Basalt fiber reinforced unsaturated polyester), GRE(Glass fiber reinforced epoxy), and GRP(Glass fiber reinforced unsaturated polyester). And then it was immersed in NaOH for 720 hours. The friction test of each specimen was conducted. The Friction coefficient analysis according to material friction depth and interfacial adhesion behavior between resin and fiber were analyzed. As a result, the mechanism of interfacial separation between resin and fiber could be analyzed. In the case of the unsaturated polyester resin with low interfacial bonding strength the longer the immersion time in the alkaline solution, the faster the internal deterioration caused by the deterioration that started from the surface, resulting in a decrease in the friction coefficient. It is hoped that this study will help to understand the degradation behavior of composite materials immersed in various chemical solutions such as NaOH, acid, and sodium hypochlorite in the future.

• Journal of the Korean Geotechnical Society
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• v.39 no.12
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• pp.61-73
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• 2023

Suction buckets are feasible options for offshore foundations to support subsea structures in deep water, enabling suction-induced installation by pumps. Recently, hybrid suction bucket foundations that combine single or multiple suction buckets with a mat foundation have been considered. The foundations effectively increase the load capacity while reducing construction costs. However, there is still insufficient experimental validation of hybrid suction bucket foundations regarding their bearing capacity. Furthermore, research on the horizontal load capacity under low vertical and moment loads is inadequate. In this study, we investigate the feasibility of using a hybrid suction bucket foundation for subsea installations in clay. We considered two types of hybrid suction bucket foundations: a circular mat with a single suction bucket and a square mat with multiple buckets. Centrifuge tests were performed to understand the hybrid suction bucket foundation characteristics under horizontal loads and their corresponding bearing capacity. Particularly, we verified the effect of the mat foundation and bucket embedment depth on the horizontal bearing mechanism and capacities. Results confirmed that the hybrid suction bucket foundation outperforms the single suction bucket.

• Journal of The Korean Society of Grassland and Forage Science
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• v.26 no.4
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• pp.177-186
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• 2006

This study was conducted to investigate the effects of the types and rates of application of animal manure on productivity of silage corn and environmental pollution in silage corn cultivation soil. The experiment was confirmed in lysimeter which was constructed with 0.30m diameter, and 1 m depth. This study was arranged in split plot design. Main plots were the types of cattle slurry (CS), swine manure fermented with sawdust (SMFS) and chemical fertilizer (CF), Subplots were the application rates of animal manure, as urea, such as 100, 200 and 400 kg N $ha^{-1}$. Dry matter(DM) and nitrogen yields of silage corn enhanced as increased application rates of CS, SMFS and CF (p<0.05). DM yield reveals that there is an decrease in order of CF>CS>SMFS (p<0.05). Crude protein (CP) contents of the whole silage corn increased as increased application rates of CS, SMFS and CF. IN addition, $NO_{3^-}N$ content in leaching water by application of animal manure reveals that there is an decrease in order SMFS>CF>CS (p<0.05). However, $NH_{4^-}N$ content was hardly influenced by application of animal manure, and $NH_{4^-}N$ content increased with application rates increased. $PO_{4^-}P$ content in leaching water by application of animal manure reveals that there is an decrease in order of SMFS>CF>CS. $PO_{4^-}P$ increased as increasing application rates (p<0.05), whereas $PO_{4^-}P$ in leaching water maintained a low levels.

• The Korean Journal of Malacology
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• v.24 no.3
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• pp.215-228
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• 2008

This study was performed to find out the community structure of macrobenthos and the environmental factors around Munseom coastal water in Jeju Island from June to December, 2007. Mean temperature and mean salinity were $19.6^{\circ}C$ and 34.03 psu, indicating stable water masses. Concentrations of DO, COD and SS were as low as those in the standard sea-water-quality classes I. Chlorophyll a concentrations ranged from 0.40 to 1.09 mg/L (mean, 0.69 mg/L), and higher concentration was observed in December rather than in June due to a blooming in winter. The mean concentration (their ranges are in parentheses) of nitrate, phosphate, and silicate were 0.15 mg/L (0.073-0.264 mg/L), 0.01 mg/L (0.004-0.011 mg/L) and 0.23 mg/L (0.039-0.464 mg/L), respectively. The values were higher near the Munseom due to influxes from the land. Of the 112 species that were identified, 40 species (36.0%) were Mollusca; 33 (28.8%) were Cnidaria; 13 (11.7%) were Porifera; 8 (7.2%) were Arthropoda and 17 species (15.3%) were others including Echinodermata. Density and biomass were estimated to be 4,340 individual/$m^2$ and $53,107.8\;gwwt/m^2$ respectively. Anthozoa was the most dominant group in abundance ($2,132\;ind./m^2$) as well as in the number of species, whereas Cnidaria was predominant in biomass ($37,630.9\;gwwt/m^2$). The dominant species were Dendronephthya gigantea, Scleronephthya gracillimum, Anthoplexaura dimorpha, Dendronephthya castanea, Thecocarpus niger, Dendronephthya spinulosa, Dendronephthya putteri, and Acabaria bicolor in the depth of 10-30 m. The seasonal variations of the number of individual and biomass of Cnidaria and Mollusca were observed. There was a slow increment in June, a decrement in October, and a drastic increasing in December. The biodiversity, evenness and richness index in surveyed stations were 2.715-3.413 (H'), 0.758-0.851(E'), and 5.202-8.720 (R) respectively. The dominance index was the highest in station M2 and the lowest in station M1.

• 한국지구물리탐사학회:학술대회논문집
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• 2002.09a
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• pp.101-125
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• 2002

A lake seismic survey was carried out to investigate possible geohazards for construction of the underground LPG storage at Namyang Lake. The proposed survey site has a land-lake combined geography and furthermore water depth of the lake is shallow. Therefore, various seismic methods such as marine single channel high resolution seismic reflection survey, sonobuoy refraction survey, land refraction survey and land-lake combined refraction survey were applied. Total survey amounts are 34 line-km of high resolution lake seismic survey, 14 lines of sonobuoy refraction survey, 890 m of land refraction survey and 8 lines of land-lake combined refraction survey. During the reflection survey, there were severe water reverberations from the lake bottom obscured subsurface profiling. These strong multiple events appeared in most of the survey area except the northern and southern area near the embankment where seems to be accumulated mainly mud dominated depositions. The sonobuoy refraction profiles also showed the same Phenomena as those of reflection survey. Meanwhile the results of the land-lake combined refraction survey showed relatively better qualities. However, the land refraction survey did not so due to low velocity soil layer and electrical noise. Summarized results from the lake seismic survey are that acoustic basement with relatively flat pattern appeared 30m below water level and showed three types of bedrock such as fresh, moderately weathered and weathered type. According to the results of the combined refraction survey, a velocity distribution pattern of the lake bottom shows three types of seismic velocity zone such as >4.5 km/s, 4.5-4.0km/s and <4.0km/s. The major fault lineament in the area showed NW-SE trend which was different from the Landsat image interpretation. A drilling was confirmed estimated faults by seismic survey.