• ALGAE
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• v.32 no.2
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• pp.101-130
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• 2017

The ichthyotoxic Cochlodinium polykrikoides red tides have caused great economic losses in the aquaculture industry in the waters of Korea and other countries. Predicting outbreak of C. polykrikoides red tides 1-2 weeks in advance is a critical step in minimizing losses. In the South Sea of Korea, large C. polykrikoides red tide patches have often been recorded offshore and transported to nearshore waters. To explore the processes of offshore C. polykrikoides red tides, temporal variations in 3-dimensional (3-D) distributions of red tide organisms and environmental parameters were investigated by analyzing 4,432 water samples collected from 2-5 depths of 60 stations in the South Sea, Korea 16 times from May to Nov, 2014. In the study area, the vegetative cells of C. polykrikoides were found as early as May 7, but C. polykrikoides red tide patches were observed from Aug 21 until Oct 9. Cochlodinium red tides occurred in both inner and outer stations. Prior to the occurrence of large C. polykrikoides red tides, the phototrophic dinoflagellates Prorocentrum donghaiense (Jun 12 to Jul 11), Ceratium furca (Jul 11 to Aug 21), and Alexandrium fraterculus (Aug 21) formed red tides in sequence, and diatom red tides formed 2-3 times without a certain distinct pattern. The temperature for the optimal growth of these four red tide dinoflagellates is known to be similar. Thus, the sequence of the maximum growth rates of P. donghaiense > C. furca > A. fraterculus > C. polykrikoides may be partially responsible for this sequence of red tides in the inner stations following high nutrients input in the surface waters because of heavy rains. Furthermore, Cochlodinium red tides formed and persisted at the outer stations when $NO_3$ concentrations of the surface waters were < $2{\mu}M$ and thermocline depths were >20 m with the retreat of deep cold waters, and the abundance of the competing red-tide species was relatively low. The sequence of the maximum swimming speeds and thus potential reachable depths of C. polykrikoides > A. fraterculus > C. furca > P. donghaiense may be responsible for the large C. polykrikoides red tides after the small blooms of the other dinoflagellates. Thus, C. polykrikoides is likely to outgrow over the competitors at the outer stations by descending to depths >20 m and taking nutrients up from deep cold waters. Thus, to predict the process of Cochlodinium red tides in the study area, temporal variations in 3-D distributions of red tide organisms and environmental parameters showing major nutrient sources, formation and depth of thermoclines, intrusion and retreat of deep cold waters, and the abundance of competing red tide species should be well understood.

• Korean Journal of Soil Science and Fertilizer
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• v.42 no.2
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• pp.103-109
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• 2009

Soils originated from limestone, located at the southern part of Kangwon province and Jecheon, Danyang of Chungbuk province are mainly composed of fine texture, and have different properties from soils originated from granite and granite gneiss, especially for water movement. This study was conducted for classification of hydrologic soil group (HSG) of soils originated from limestone by measuring the infiltration rate of surface soils and percolation rate of sub soils. Soils used for the experiment were 6 soils in total : Gwarim, Mosan, Jangseong, Maji, Anmi and Pyongan series. Infiltration and percolation rate were measured by a disc tension infiltrometer and a Guelph permeameter, respectively. Particle size distribution and organic matter content of the soils were analyzed. HSG, which was made by USDA NRCS(National Resources Conservation Service) for hydrology, of Gwarim series with O horizon of accumulated organic matter was classified as type A which show the properties of low runoff potential, rapid infiltration and percolation rate. HSG of Mosan series, which has high gravel content and very rapid permeability, was classified as type B/D because of the impermaeble base rock layer under 50cm from surface. HSG of Jangseong series with shallow soil depth was classified as type C/D owing to the impermaeble base rock layer under 50cm from surface. HSG of Maji series was type B, and HSG of Anmi series used as paddy land was type D because of slow infiltration and percolation rate caused by the disturbance of surface soil by puddling. HSG of Pyeongan series having a sudden change of layer in soil texture was type D because of the slow percolation rate caused a the layer.

• Journal of the Korean Wood Science and Technology
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• v.24 no.1
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• pp.34-47
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• 1996

Veneers of two nominal thicknesses, 1.5 and 2.5mm, were rotary peeled from Japanese larch (Larix leptolepis). Dahurian larch (Larix gmelinei) and Radiata pine (Pinus radiata) bolts unheated and heated in the water vat temperature of $66^{\circ}C$ by rising a final temperature at 10cm core of $60^{\circ}C$ to remain core diameter of 11.4cm. 1.5 and 2.5mm thick veneer cut from the heated Japanese larch were significantly thinner than those of the unheated bolt and 2.5mm thick veneer cut from the heated Dahurian larch were significantly thicker than that of the unheated bolt. 1.5mm thick Dahurian larch veneer and 1.5 and 2.5mm thick Radiata pine veneers showed insignificant difference between the unheated and heated bolts, respectively. Check distance on the loose side of 1.5mm thick veneer cut from the heated Radiata pine was significantly wider than that of the unheated bolt. However check distances on the loose side of 1.5 and 2.5mm thick Japanese larch and Dahurian larch veneers and 2.5mm thick Radiata pine veneers showed insignificant difference between the unheated and heated bolts. Also the depth of check on the loose side of three species showed insignificantly difference between the unheated and heated bolts. Arithmatic mean deviation($R_a$) and maximum height($R_{max}$) of the profile on the loose side of dried veneer by preheating the bolt compared with unheated bolts were different among apecies and between veneer thickness. The preheating treatment slightly affected qualities of these thin veneers such as 1.5 and 2.5mm. The yield of 2.5mm thick veneer from the heated radiata pine was significantly higher than that of the unheated bolt. However the yield of 2.5mm thick veneer for other two species and 1.5mm thick veneer for three species showed insignificant difference between the unheated and heated bolts. The yield of 2.5mm thick veneer for three species were higher than those of 1.5mm thick veneer. The average yields of green veneer of Japanese larch. Dahurian larch and Radiata pine were 57.1, 55.1 and 54.0 percent, respectively. Variables such as initial MC. drying time and veneer thickness had strong effect for Japanese larch veneer, less effect for Radiata pine veneer and nuch less effect on final MC for Dahurian larch veneer in jet drying. Correlation between the current MC and the drying time of Dahurian larch with low variation of initial MC was higher than those of Japanese larch and Radiata pine veneer with high variation of initial MC in high temperature drying. Thickness shrinkages of 2.5mm thick veneer for Japanese larch and Radiata pine were higher than those of 1.5mm thick veneers, but shrinkages of Dahurian larch veneer were similar between two nominal veneer thicknesses.

• Korean Journal of Environment and Ecology
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• v.21 no.1
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• pp.55-66
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• 2007

This study was conducted to analyze the distribution patterns of wintering waterbird communities in relation to local environmental factors in the urban streams of Seoul, Korea. A field survey was conducted at 66 sites of 5 tributaries and the main channel of the Hangang River in Seoul in January 2006. The total of 65 species and 39,560 individuals were recorded in the field survey. There were 48 species and 28,989 individuals in the Hangang River, 14 species and 1,395 individuals in the Tancheon stream, 15 species and 2,306 individuals in the Jungrangcheon stream, 22 species and 5,990 individuals in the Anyangcheon, 18 species and 283 individuals in the Changrungcheon stream, and 24 species and 597 individuals in Gokrungcheon stream. The dominant species were Anas platyrhynchos (22.65%), A. poecilorhyncha (14.01%), Aythya ferina (13.26%), Aythya fuligula (8.04%), and Mergus merganser (7.03%). Among the 16 species (with 30,650 individuals) of ducks, the dabbling and diving ducks were 8 species with 18,286 individuals and 8 species with 12,364 individuals, respectively. Through the principal component analysis, the study sites were classified into four main groups according to the similarity of their waterbirds' species compositions: 3 tributaries in the urban area (Group 1), 2 tributaries in the rural area (Group 2), one in the rural area, one in the urban area, the urban area in Hangang River (Group 3) and the main channel of the Hangang River in the urban area (Group 4). Species diversity index and species evenness were the highest in Group 1, while the lowest Group 2. Analysis on their environmental factors showed that the waterbirds wintering in urban streams of Seoul prefer broad water width, low water depth and broad resting sites.

• Korean Journal of Environmental Agriculture
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• v.38 no.1
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• pp.23-33
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• 2019

BACKGROUND: The golden apple snail(GAS, Pomacea canaliculata Lamarck) is an invasive freshwater snail. It has occurred 34 years since the introduction of the GAS to the Korea. The GASs have been used recently for weed control in wet rice cultivation. The GASs'adaptability to the environment of GAS has been improved and the GASs devour the young stage of the crops as well as weeds. METHODS AND RESULTS: We surveyed the survival area of the snails throughout the country during the winter seasons from 2000 to 2017 and crop damage due to GASs in 2017. Local maximum, minimum, and average air temperatures were monitored daily. The surveyed regions for the survival of the GASs in winters were Gangjin, Goheung, Shinan, Haenam, Gimhae, Haman, Busan, Jeju, and Seogwipo. The survival durations at low temperatures were 12 hours at $-5^{\circ}C$, 1 day at $-3^{\circ}C$, 2 days at $-1^{\circ}C$, 10 days at $0^{\circ}C$, and over 30 days at $3^{\circ}C$. The eggs of GASs were not able to overwinter. The overwintering condition of the GAS needed a water depth of 10-20 cm with well formed mud. Crop damages caused by the overwintering GASs occurred in rice and water dropwort. CONCLUSION: The overwintering GAS was first identified in Haenam, South Korea 2000 after introduction of the GAS. The overwintering area of GAS expanded to the mid-southern parts of Korea. We propose that it has not yet become a pest to rice or any other crop.

• Ecology and Resilient Infrastructure
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• v.9 no.3
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• pp.183-193
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• 2022

The growth inhibitory effect of Microcystis aeruginosa according to the ultrasonic irradiation time was evaluated using a large algae sample volume (10 L) for various ultrasonic irradiation times (0.5, 1, 1.5, 2, 2.5 and 3 hr) at a laboratory scale. Based on the analysis of Chl-a and cell number of M. aerginosa, algae growth inhibition was observed with the decrease in Chl-a and cell number in all experimental groups after the ultrasonic irradiation. For the experimental group (T_B, T_C, T_D) with an ultrasonic irradiation time of less than 2 hours, rapid regrowth of algae was observed after growth inhibition, but the experimental group (T_E, T_F, T_G) with an irradiation time of more than 2 hours successfully inhibited algal growth lasting one or two more days. Based on the comparison of the recovery time to initial cell number the experimental group (T_B, T_C, T_D) took less than 20 days whereas the experimental group (T_E, T_F, T_G) took about 30 days. Correspondingly, the experimental group showed a high first order decay rate (𝜅) in proportion to the ultrasonic irradiation time during the growth inhibition period. Additionally, the specific growth rates (𝜇) during regrowth in the experimental group with irradiation time of more than 2 hours were relatively low compared to those in the experimental group with less than 2 hours. Therefore, ultrasonic irradiation for more than 2 hours is required for long-term (30 days) inhibition of algal growth in stagnant waters. However, the appropriate ultrasonic irradiation time for algae growth inhibition should be determined according to various field conditions such as the volume of stagnant water, water depth, flow rate, algae concentration, etc. Finally, damages to the algal cell surface and cell membrane were clearly observed, and both destruction and disturbance of gas vesicles of M. aeruginosa in the experimental group were discovered, indicating the growth inhibitory effect of Microcystis aeruginosa according to the ultrasonic irradiation time was confirmed.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.6
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• pp.327-340
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• 2017

This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2016. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) The research works on the thermal and fluid engineering have been reviewed as groups of flow, heat and mass transfer, the reduction of pollutant exhaust gas, cooling and heating, the renewable energy system and the flow around buildings. CFD schemes were used more for all research areas. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the results of the long-term performance variation of the plate-type enthalpy exchange element made of paper, design optimization of an extruded-type cooling structure for reducing the weight of LED street lights, and hot plate welding of thermoplastic elastomer packing. In the area of pool boiling and condensing, the heat transfer characteristics of a finned-tube heat exchanger in a PCM (phase change material) thermal energy storage system, influence of flow boiling heat transfer on fouling phenomenon in nanofluids, and PCM at the simultaneous charging and discharging condition were studied. In the area of industrial heat exchangers, one-dimensional flow network model and porous-media model, and R245fa in a plate-shell heat exchanger were studied. (3) Various studies were published in the categories of refrigeration cycle, alternative refrigeration/energy system, system control. In the refrigeration cycle category, subjects include mobile cold storage heat exchanger, compressor reliability, indirect refrigeration system with $CO_2$ as secondary fluid, heat pump for fuel-cell vehicle, heat recovery from hybrid drier and heat exchangers with two-port and flat tubes. In the alternative refrigeration/energy system category, subjects include membrane module for dehumidification refrigeration, desiccant-assisted low-temperature drying, regenerative evaporative cooler and ejector-assisted multi-stage evaporation. In the system control category, subjects include multi-refrigeration system control, emergency cooling of data center and variable-speed compressor control. (4) In building mechanical system research fields, fifteenth studies were reported for achieving effective design of the mechanical systems, and also for maximizing the energy efficiency of buildings. The topics of the studies included energy performance, HVAC system, ventilation, renewable energies, etc. Proposed designs, performance tests using numerical methods and experiments provide useful information and key data which could be help for improving the energy efficiency of the buildings. (5) The field of architectural environment was mostly focused on indoor environment and building energy. The main researches of indoor environment were related to the analyses of indoor thermal environments controlled by portable cooler, the effects of outdoor wind pressure in airflow at high-rise buildings, window air tightness related to the filling piece shapes, stack effect in core type's office building and the development of a movable drawer-type light shelf with adjustable depth of the reflector. The subjects of building energy were worked on the energy consumption analysis in office building, the prediction of exit air temperature of horizontal geothermal heat exchanger, LS-SVM based modeling of hot water supply load for district heating system, the energy saving effect of ERV system using night purge control method and the effect of strengthened insulation level to the building heating and cooling load.

• Korean Journal of Soil Science and Fertilizer
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• v.9 no.2
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• pp.99-105
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• 1976

After investigation of soil characteristics the properties of a reclaimed marine soil (Gupo series) distributed along the southern coastal areas of Korea are summarized as follows: 1. Gupo soils distributed in the southern Ria coastal area are derived from rolling to hilly materials and are poorly sorted with less influences of river fluvial action. These soils have high content of sand compared with the broad fluvio-marine soils in the western coastal areas. 2. The morphological features of the poorly drained Gupo soils are greyish brown sandy loam with a few yellowish mottles in the surface horizon and are grey sandy loam with a few gravel in the sub-strata. The ground water table remains around 10-30cm below the surface. These soils, recently reclaimed younger deposits, do not show any evidence of illuviation. 3. The "n" value (about 0.8) of the Gupo soils indicates physically unripened soils. 4. pH value of these soils shows more than 8.0 throughout the profile. Organic matter contents are extremely low (around 0.5%) except 1.2 percent in the surface horizon. C.E.C. ranges from 7 to 9m.e/100g which is lower than average in the country. The ratios of extractable cations such as Ca, Mg, Na and K of the surface horizon are 20:7:4:1. Base saturation is more than 60%. Available phosphate content is very low that is less than 25 ppm. Electric conductivity of the soils at $25^{\circ}C$ ranges 7 to 12 mmhos/cm and increased with depth. 5. According to classification of soil based on physical ripening, the Gupo soils can be classified into "Unripe soils with half-ripe sub-soils". The soils could be classified into "Hydric Haplaquents" in the original of the 7th Approximation (1960), but into "Typic Haplaqents in the supplement of 7th approximation which the physical ripening condition is not clearly expressed. Soil Taxonomy, apparently the final version of the 7th approximation, defines the soils as "Haplic Hydraquents" that clearly show the condition of physical ripening as well as other properties. Other several classification systems applied do not describe physical ripening condition of the soils.

• Korean Journal of Environmental Biology
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• v.37 no.4
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• pp.726-734
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• 2019

To understand the relationship between water velocity in a fishway and fish morphology, the fineness ratio of fish, expressed as the standard length to the body depth, was measured. The fineness ratios of fish groups belonging to Cyprinidae, Acheilognathinae, Centropomidae, and Centrachidae were relatively low. The FRs of other groups, excluding eel-shaped types of fish, were over 4.5, indicating streamlined structures. The fineness ratios of Korean fish were classified into three different types: type I was Bitterling-Carp group that favored a slow-flowing pool habitat(FRs ranged from 2.1 to 3.3), type II was the Chub group representing streamlined types (FRs FRs ranged from 3.7 to 5.2), and type III was the Smelt-Barbel fish group that preferred riffle-run habitats with high velocity (FRs is over 5.2). Fish abundance analysis of fish using the fishway during the experimental periods showed a relatively high abundance of both type II and III compared to type I. The FRs of the fish passing through fishway(velocity 0.5-1.0 m s^-1) ranged from 4.5 to 5.0, indicating that the fish using the fishway were mainly the streamlined type. As one of the standard fishways in Korea, the flow rate of the ice harbor type ranged from 0.2 to 2.6 m s^-1. The FR values of the fish groups using the fishway ranged from 4.3 to 5.0. In contrast, the flow rate measured in an artificial channel type of fishway (same as a natural type of fishway) ranged from 0.1 to 1.9 m s^-1 and the FR values for the fish groups using a natural type of fishway ranged from 3.3 to 5.3. The low FR values in natural fish are considered to be due to differences in the flow rates between the two types of fishways.

• Korean Journal of Ecology and Environment
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• v.37 no.1 s.106
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• pp.1-11
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• 2004

The limnological characteristics of a coastal lagoon were studied in Lake Hyangho, one of a series of brackish lagoons along the eastern coast of Korea. Phytoplankton community structure, physical factors, and chemical factors were surveyed from May 1998 through November 2002 on a two-month interval basis. Temperature, salinity, Secchi disc transparency, TN, TP, organic matter content of sediment, chlorophyll a concentration, dominant phytoplankton species, and phytoplankton cell density were measured. Salinity gradient was formed between the overlying freshwater stream water and the permeated seawater at the bottom. The chemocline was persistent at the depth of 2 ${\sim}$ 5 m that caused discontinuities of salinity, DO, and temperature profiles. The inversion of vertical temperature profiles with higher temperature in deeper layer was observed in early winter. Secchi disc transparency was very low with the range of 0.1 to 1.1m. TP, TN, and Chl. a concentration in the epilimnion was 0.011 ${\sim}$ 0.238 mgP $L^{-l}$, 0.423 ${\sim}$ 2.443 mgN $L^{-l}$, and 0.7 ${\sim}$ 145.2 mg $m^{-3}$, respectively. Sediment was composed of silt and coarse silt. COD, TP, and TN content of dry sediment were 19.7 ${\sim}$ 73.3 mg$O_2\;g^{-1}$, 0.61 ${\sim}$ 1.32 mgP $g^{-l}$ and 0.64 ${\sim}$ 0.88 mgN $g^{-l}$, respectively. Dominant phytoplankton species were chlorophytes (Ankistrodesmus falcatus) and cyanobacteria (Oscillatoria sp. and Merismopedia tennuissima). The total cell density was in the range of 560 ${\sim}$ 35,255 cells $mL^{-l}$.