• Clean Technology
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• v.28 no.3
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• pp.218-226
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• 2022

As a result of the recent social transformation towards a hydrogen economy and carbon-neutrality, the demands for hydrogen energy have been increasing rapidly worldwide. As such, eco-friendly hydrogen production technologies that do not produce carbon dioxide (CO₂) emissions are being focused on. Among them, ammonia (NH₃) is an economical hydrogen carrier that can easily produce hydrogen (H₂). In this study, Ru/Al₂O₃ catalyst coated onmetallic monolith for hydrogen production from ammonia was prepared by a dip-coating method using a catalyst slurry mixture composed of Ru/Al₂O₃ catalyst, inorganic binder (alumina sol) and organic binder (methyl cellulose). At the optimized 1:1:0.1 weight ratio of catalyst/inorganic binder/organic binder, the amount of catalyst coated on the metallic monolith after one cycle coating was about 61.6 g L^-1. The uniform thickness (about 42 ㎛) and crystal structure of the catalyst coated on the metallic monolith surface were confirmed through scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. Also, a numerical optimization regression equation for NH3 conversion according to the independent variables of reaction temperature (400-600 ℃) and gas hourly space velocity (1,000-5,000 h^-1) was calculated by response surface methodology (RSM). This model indicated a determination coefficient (R²) of 0.991 and had statistically significant predictors. This regression model could contribute to the commercial process design of hydrogen production by ammonia decomposition.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.5
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• pp.721-734
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• 2022

This study analyzed the spatio-temporal variation characteristics of major environmental factors such as primary productivity (PP), chlorophyll a, nutrients, sinking particle matters, and organic contamination and biochemical composition of surface sediment on a monthly basis for approximately 2 years around shellfish mariculture in Jaran Bay, Korea. In addition, PP in Jaran Bay was compared with that in other coastal areas and related policy plans were proposed. The average PP of the study area was high in summer and autumn with 6.43~115.43 mgC m^-2 hr^-1 range. This was lower than that in Gamak Bay and Masan Bay, whereas higher than that in Garorim Bay and the West Sea. The PP in coastal waters, where many aquaculture farms were distributed, significantly fluctuated. The different size compositions of phytoplanktons constituting chlorophyll a slightly varied by month, and little restriction existed on the productivity of phytoplanktons owing to the depletion of nutrients. Typically, the Redfield ratio was less than 16, indicating that nitrogen was the limiting factor for the growth of phytoplanktons. The biochemical composition of particulate organic matters in the water column showed the highest carbohydrates, but lipids and protein contents were high in surface sediments. The concentration of TOC and AVS of the surface sediments was high at inside of bay, and sometimes, exceeded the environmental criteria of fishing grounds. The organic C:N ratio of sediments ranged from 8.1 to 10.4 on average. PP had the highest correlation with chlorophyll a, nitrogen and protein of particle organic materials. Recently, chlorophyll a, DIN, and DIP of water column trends tended to decrease, however, the contamination of sediments increased. Considering the annual PP of 125.9 gC m^-2 yr^-1 and mariculture area (oyster) of 4.97 km², the annual carbon production from phytoplanktons was estimated to be about 625 tons, and the annual total wet weight of shellfish (oyster) was estimated to be about 6,250 tons.

• Journal of Preventive Medicine and Public Health
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• v.32 no.1
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• pp.30-39
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• 1999

Objectives. This study was carried out to evaluate hearing impairment judgement and to investigate the differences in various diagnostic criteria for noise-induced hearing loss (NIHL) among workers who required for close observation (C). Methods. Out of 731,029 workers who had taken the specific periodic health examination in 1994, we used the audiometric data on 37,999 workers (C) eliminating the employees who had previous otologic problems. Many investigators have being using different criteria for the evaluation of hearing impairment. In this study, we used the criteria of early (1989-1994), current, compensation for NIHL in Korea, 2-, 3-, 4-divided classification and hearing loss at 4,000 Hz and compared the evaluation results. Results. The prevalences of C and workers who had occupational disease $(D_1)$ diagnosed for NIHL were 11.1 % and 0.44 %. There were significant difference in the prevalences of C and $D_1$, depending on different province of Korea. Pure tone averages (PTAs) were not appropriately applied in their evaluation 97% of workers whom we studied on were below the level of mild hearing loss judged by ISO standard. However, there were wide variations in the prevalence rate of mild hearing loss by diagnostic criteria. Thus, there were different judgements in determining the degree of NIHL depending on which diagnostic criteria were utilized. PTAs were found 20.54 (Rt) and 20.74 (Lt) when the method of 3-divided classification was applied for audiometric data. The degree of hearing impairment of the left ear was more severe than that of right ear. The prevalence of normal hearing threshold below 20 dB was 75.4% and the range of difference in both ear was below 10 dB. Right sided hearing threshold levels were 21.08 dB (500 Hz), 18.44 dB (1,000 Hz), 22.09 (2,000 Hz) and 52.36 dB (4,000 Hz). There was typical high frequency loss (C5-dip at 4,000 Hz) above 30 - 40 dB in normal hearing level. The increasing trend in hearing threshold level was gradually decreased by the increase of PTAs. The difference between PTAs and threshold at 4,000 Hz was about 10 dB. Conclusions. We could found that PTAs in the previous examination were not appropriately evaluated. This study revealed that they did not use unique criteria for managing the workers of NIHL. For the prevention of NIHL, it was found that the quality control on diagnosis and comprehensive management program were required, especially for those of hearing loss (C).

• Korean Journal of Fisheries and Aquatic Sciences
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• v.34 no.5
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• pp.536-544
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• 2001

Three harmful algal bloom species with similar morphology, Cochlodinium polykrikoides, Gyodinium impudicum and Gymodinium catenatum have damaged to aquatic animals or human health by either making massive blooms or intoxication of shellfishes in a food chain. Eco-physiological and hydrodynamic studies on the harmful algae offer useful informations in the understanding their bloom mechanism by giving promising data for the prediction and modelling of harmful algal blooms event. Thus, we studied the abundance of these species in the coastal area of South Sea of Korea and their effects of temperature, salinity, irradiance and nutrient on the growth for the isolates. The timing for initial appearance of the three species around the coastal area of Namhaedo, Narodo and Wando was between Bate July and late August in 1999 when water temperature ranged from $22.8^{\circ}C\;to\;26.5^{\circ}C$ Vegetative cells of C. polykrikoides and G. impudicum were abundant until late September when water temperature had been dropped to less than $23^{\circ}C$. By contrast, vegetative cell of G. catenatum disappeared before early September, showing shorter period of abundance than the other two species in the South Sea. Both G. impudicum and G. catenatum revealed comparatively low density with a maximal cell density of 3,460 cells/L and 440 cells/L, respectively without making any bloom, while C. polykrikoides made massive blooms with a maximal cell density more than $40\times10^6$cells/L, The three species showed a better growth at the relatively higher water temperature ranging from 22 to $28^{\circ}C$ with their maximal growth rate at $25^{\circ}C$ in culture, which almost corresponded with the water temperature during the outbreak of C. polykrikoides in the coastal area of South Sea. Also, they all showed a relatively higher growth at the salinity from 30 to $35\%$. Specially, G. impudicum showed the euryhalic characteristics among the species, On the other hand, growth rate of G. catenatum decreased sharply with the increase of water temperature at the experimental ranges more than $35\%$. The higher of light intensities showed the better growth rates for the three species, Moreover, C. polykrikoides and G. impudirum continued their exponential growth even at 7,500 lux, the highest level of light intensity in the experiment, Therefore, It is assumed that C. polykrikoides has a physiological capability to adapt and utilize higher irradiance resulting in the higher growth rate without any photo inhibition response at the sea surface where there is usually strong irradiance during its blooming season. Although C. poiykikoides and G. impudicum continued their linear growth with the increase of nitrate ($NO_3^-$) and ammonium ($NH_4^-$) concentrations at less than the $40{\mu}M$, they didn't show any significant differences in growth rates with the increase of nitrate and ammonium concentrations at more than $40{\mu}M$, signifying that the nitrogen critical point for the growth of the two species stands between 13.5 and $40{\mu}M$. Also, even though both of the two species continued their linear growth with the increase of phosphate ($PO_4^{2-}$) concentrations at less than the $4.05{\mu}M$, there were no any significant differences in growth rates with the increase of phosphate concentrations at more than $4.05{\mu}M$, signifying that the phosphate critical point for the growth of the two species stands between 1.35 and $4.05{\mu}M$. On the other hand, C. polykrikoides has made blooms at the oligotrophic environment near Narodo and Namhaedo where the concentration of DIN and DIP are less than 1.2 and $0.3{\mu}M$, respectively. We attributed this phenomenon to its own ecological characteristics of diel vertical migration through which C. polykrikoides could uptake enough nutrients from the deep sea water near bottom during the night time irrespective of the lower nutrient pools in the surface water.

• Economic and Environmental Geology
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• v.44 no.5
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• pp.413-431
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• 2011

An Epithemal Au-Ag mineralized zone is developed in the Moisan area of Hwangsan-myeon, Haenam-gun, Jeol-lanam-do, Korea, which is located in the southwestern part of the Ogcheon metamorphic zone. It is hosted in the Hwangsan volcaniclastics of the Haenam Formation of the Late Cretaceous Yucheon Group. This research investigated the characteristics of bedding arrangement, fold, fault, fracture system, quartz vein and the time-relationship of the fracture system to understand the geological structure related to the formation of the mineralized zone. On the basis of this result, the tectonic environment at the time of the mineralization was considered. Beds mainly trend east-northeast and gently dip into north-northwest or south-southeast. Their poles have been rearranged by subhorizontal-upright open fold of (east)-northeast trend as well as dip-slip fault. Fracture system was formed through at least 6~7 different deformation events. D1 event; formation phase of the main fracture set of EW (D1-1) and NS (D1-2) trends with a good extensity, D2 event; that of the extension fracture of NW trend, and conjugate shear fracturing of the EW (dextral) and NS (sinistral) trends, D3 event; that of the extension fracture of NE trend, and conjugate shear refracturing of the EW (sinistral) and NS (dextral) trends, D4 event; that of the extension fracture of NS trend showing a poor extensity, D5 event; that of the extension fracture of NW trend, and conjugate shear refracturing of the EW (dextral) and NS (sinistral) trends, D6 event; that of the extension fracture of EW trend showing a poor extensity. Frequency distribution of fracture sets of each deformation event is D1-1 (19.73 %)> D1-2 (16.44 %)> D3=D5 (14.79 %)> D2 (13.70 %)> D4 (12.33 %)> D6 (8.22 %) in descending order. The average number of fracture sets within 1 meter at each deformation event is D6 (5.00)> D5 = D4 (4.67)> D2 (4.60)> D3 (4.13)> D1-1 (3.33)> D1-2 (2.83) in descending order. The average density of all fractures shows 4.20 fractures/1 m, that is, the average spacing of all fractures is more than 23.8 cm. The frequency distribution of quartz veins at each orientation is as follows: EW (52 %)> NW (28 %)> NS (12 %)> NE (8 %) trends in descending order. The average density of all quartz veins shows 4.14 veins/1 m, that is, the average spacing of all quartz veins is more than 24.2 cm. Microstructural data on the quartz veins indicate that the epithermal Au-Ag mineralization (ca. 77.9~73.1 Ma) in the Moisan area seems to occur mainly along the existing D1 fracture sets of EW and NS trends with a good extensity not under tectonic stress but non-deformational environment directly after epithermal rupture fracturing. The D1 fracturing is considered to occur under the unstable tectonic environment which alternates compression and tension of NS trend due to the oblique northward subduction of the Izanagi plate resulting in the igneous activity and deformation of the Yucheon Group and the Bulguksa igneous rocks during Late Cretaceous time.

• Geophysics and Geophysical Exploration
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• v.13 no.1
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• pp.40-50
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• 2010

The building process of any geological map involves linking sparse lithological outcrop information with equally sparse geometrical measurements, all in a single entity which is the preferred interpretation of the field geologist. The actual veracity of this interpretative map is partially dependent upon the frequency and distribution of geological outcrops compounded by the complexity of the local geology. Geophysics is commonly used as a tool to augment the distribution of data points, however it normally does not have sufficient geometrical constraints due to: a) all geophysical inversion models being inherently non-unique; and b) the lack of knowledge of the physical property contrasts associated with specific lithologies. This contribution proposes the combined use of geophysical edge detection routines and 'three point' solutions from topographic data as a possible approach to obtaining geological contact geometry information (strike and dip), which can be used in the construction of a preliminary geological model. This derived geological information should first be assessed for its compatibility with the scale of the problem, and any directly observed geological data. Once verified it can be used to help constrain the preferred geological map interpretation being developed by the field geologist. The method models the contacts as planar surfaces. Therefore, it must be ensured that this assumption fits the scale and geometry of the problem. Two examples are shown from folded sequences at the Bathurst Mining Camp, New Brunswick, Canada.

• Journal of the Korean Society of Marine Environment & Safety
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• v.19 no.4
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• pp.315-326
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• 2013

This study investigated the temporal-spatial distribution and variations in water quality parameters (temperature, salinity, pH, DO, COD, SPM, DIN, DIP, silicate, TN, TP, and chlorophyll-a) in the coastal area of Jeju, Korea, adjacent to aquaculture ponds (Aewol-ri, Haengwon-ri, Pyosun-ri, and Ilkwa-ri). Data were collected bimonthly from February 2010 to December 2011. A principal component analysis (PCA) identified three major factors controlling variations in water quality during the sampling period. Aquaculture effluent water led to large changes in nutrient levels. The highest nutrient values were observed during the investigation period. The relatively large increase in organic matter at the sampling stations coupled with sea area runoff events during the summer rainy period. Variation in chlorophyll-a concentration was mainly driven by meteorological factors such as air temperature and rainfall in the coastal areas of Aewol and Haengwon. In the coastal areas of Pyosun and Ilkwa, pollution was caused by anthropogenic factors such as discharge of aquaculture effluent water. High nutrient concentrations at the majority of the coastal stations indicate eutrophication of coastal waters, especially within a distance of 300 m and depth of 10m from drainage channels. Coastal eutrophication driven by aquaculture effluent may be harmful inshore. Events such as eutrophication may potentially influence water pollution in aquaculture ponds when seawater intake is detected because of aquaculture effluent water.

• Research in Plant Disease
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• v.20 no.1
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• pp.54-58
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• 2014

Anthracnose crown rot (ACR), caused by Colletotrichum fructicola, is a serious disease of strawberry in Korea. The primary inoculums of ACR were symptomless strawberry plants, plant debris, and other host plants. To effectively control anthracnose in symptomless transplanted strawberries, it is necessary to use disease-free plants, detect the disease early, and apply a fungicide. Therefore, in 2010 and 2011, we evaluated the efficacy of pre-plant fungicide dips by using strawberry transplants infected by C. fructicola for the control of anthracnose. Dipping plants in prochloraz-Mn for 10 min before planting was most effective for controlling anthracnose in symptomless strawberry plants and resulted in more than 76% control efficacy. Azoxystrobin showed a control efficacy of over 40%, but plants treated with pyraclostrobin, mancozeb and iminoctadine tris showed high disease severity. The control efficacy of the dip treatment with prochloraz-Mn did not differ with temperature and time. Treatment with prochloraz-Mn for more than an hour caused growth suppression in strawberry plants. Therefore, the development of anthracnose can be effectively reduced by dipping strawberry plants for 10 min in prochloraz-Mn before planting.

• Journal of Astronomy and Space Sciences
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• v.31 no.1
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• pp.15-23
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• 2014

We present preliminary observations of the field-aligned-irregularities (FAIs) in the E and F regions during the solar minimum (2009 - 2010) using the 40.8 MHz coherent backscatter radar at Daejeon ($36.18^{\circ}N$, $127.14^{\circ}E$, $26.7^{\circ}N$ dip latitude) in South Korea. The radar, which consists of 24 Yagi antennas, observes the FAIs using a single beam with a peak power of 24 kW. The radar has been continuously operated since December 2009. Depending on the manner of occurrence of the backscatter echoes, the E-region echoes are largely divided into two types: quasi-periodic (QP) and continuous echoes. Our observations show that the QP echoes occur frequently above an altitude of 105 km in the post-sunset period and continuous echoes occur preferentially around an altitude of 105 km in the post-sunrise period. QP echoes appear as striated discrete echoes for a period of about 10 - 20 min. The QP-type echoes occur more frequently than the continuous-type echoes do and the echo intensity of the QP type is stronger than that of the continuous type. In the F region, the FAIs occur at night at an altitude interval of 250 - 450 km. As time proceeds, the occurrence height of the FAIs gradually increases until early in the morning and then decreases. The duration of the F-region FAIs is typically a few hours at night, although, in rare cases, FAIs persist throughout the night or appear even after sunrise. We discuss the similarities and differences of the FAIs observed by the Daejeon radar in comparison with other radar observations.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.42 no.2
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• pp.90-98
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• 2016

Objectives: The aim of this study was to compare the osteogenic effects of demineralized dentin matrix (DDM) combined with recombinant human bone morphogenetic protein-2 (rhBMP-2) in rabbit calvarial defects with DDM and anorganic bovine bone (ABB) combined with rhBMP-2. Materials and Methods: Four round defects with 8-mm diameters were created in each rabbit calvaria. Each defect was treated with one of the following: 1) DDM, 2) ABB/rhBMP-2, or 3) DDM/rhBMP-2. The rhBMP-2 was combined with DDM and ABB according to a stepwise dry and dip lyophilizing protocol. Histological and microcomputed tomography (${\mu}CT$) analyses were performed to measure the amount of bone formation and bone volume after 2- and 8-week healing intervals. Results: Upon histological observation at two weeks, the DDM and ABB/rhBMP-2 groups showed osteoconductive bone formation, while the DDM/rhBMP-2 group showed osteoconductive and osteoinductive bone formation. New bone formation was higher in DDM/rhBMP-2, DDM and ABB decreasing order. The amounts of bone formation were very similar at two weeks; however, at eight weeks, the DDM/rhBMP-2 group showed a twofold greater amount of bone formation compared to the DDM and ABB/rhBMP-2 groups. The ${\mu}CT$ analysis showed markedly increased bone volume in the DDM/rhBMP-2 group at eight weeks compared with that of the DDM group. Notably, there was a slight decrease in bone volume in the ABB/rhBMP-2 group at eight weeks. There were no significant differences among the DDM, ABB/rhBMP-2, and DDM/rhBMP-2 groups at two or eight weeks. Conclusion: Within the limitations of this study, DDM appears to be a suitable carrier for rhBMP-2 in orthotopic sites.