• Journal of Korea Water Resources Association
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• v.55 no.1
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• pp.99-109
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• 2022

This study was intended to suggest the applicability of stepped boulder fishway using the concept of traditional boulder weir, focusing on the problems of existing concrete pool-and-weir fishways installed in mountain streams. To achieve this purpose, a stepped boulder fishway was designed and constructed as a pilot project in consideration of ascending capacity of the selected target fishes. Under the given discharge conditions, the hydraulic characteristics of the fishway were investigated in the field, and the characteristics and ascending capacity of the fishes were compared and analyzed. The fishway had a short length and steep slope, but the mean drops between each baffle were the range of 0.15 to 0.29 m, and this range satisfied the limit condition of about 0.40 m, which was in the limit of the drop that target fishes can ascend. The mean velocities of each baffle and pool were 0.82 to 0.87 m/sec and 0.13 to 0.24 m/sec. This result satisfied the conditions of burst speed (10 to 30 times of body length) and mean velocity of the resting pool (7 to 25% of burst speed) for target fishes. Since the bottom surface of the pool formed of boulders had a gentle reverse slope and rotational flow did not occur, the efficiency of fishway can be increased, and it will also be possible to solve the maintenance problem by flushing bed materials.

• Journal of the Korean Institute of Gas
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• v.25 no.6
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• pp.22-28
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• 2021

Combustion characteristics were examined experimentally for a swirl-stabilized double cone premixed burner nozzle used for industrial gas turbines for power generation. An original model and a variant with a different fuel injection pattern are tested to compare their combustion characteristics such as NOx, CO and stability in pressurized conditions with single burner-flame and in an ambient multi-flame conditions with multi-burners. Test results show that NOx emissions are smaller for the variant, whose number of fuel holes is reduced with the same total area of fuel holes, in ambient and pressurized single-flame conditions with single burner, which results from enhanced fuel/air mixing due to a higher penetration of fuel into the air stream. The multi-burnerflame test results show that NOx emissions are smaller for the variant due to reduced flame interactions, which, on the contrary, slightly reduces the stability margin. On-site test results fromin an actual power plants also show that NOx emissions are reduced for the variant, compared with the original one, which is in agreement with the lab test results stated above.

• Korean Journal of Agricultural and Forest Meteorology
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• v.23 no.4
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• pp.222-234
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• 2021

Airborne-pests can be introduced into Korea from overseas areas by wind, which can cause considerable damage to major crops. Meteorological models have been used to estimate the wind trajectories of airborne insects. The objective of this study is to analyze the effect of input settings on the prediction of areas where airborne pests arrive by wind. The wind trajectories were predicted using the HYbrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model. The HYSPLIT model was used to track the wind dispersal path of particles under the assumption that brown plant hopper (Nilaparvata lugens) was introduced into Korea from sites where the pest was reported in China. Meteorological input data including instantaneous and average wind speed were generated using meso-scale numerical weather model outputs for the domain where China, Korea, and Japan were included. In addition, the calculation time intervals were set to 1, 30, and 60 minutes for the wind trajectory calculation during early June in 2019 and 2020. It was found that the use of instantaneous and average wind speed data resulted in a considerably large difference between the arrival areas of airborne pests. In contrast, the spatial distribution of arrival areas had a relatively high degree of similarity when the time intervals were set to be 1 minute. Furthermore, these dispersal patterns predicted using the instantaneous wind speed were similar to the regions where the given pest was observed in Korea. These results suggest that the impact assessment of input settings on wind trajectory prediction would be needed to improve the reliability of an approach to predict regions where airborne-pest could be introduced.

• Korean Journal of Ichthyology
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• v.33 no.4
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• pp.252-261
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• 2021

The egg development and early life history of short barbel gudgeon Squalidus japonicus coreanus were investigated. For the experiments, the mature adults were collected at the stream Jicheon in Korea. The eggs from the females were obtain by injecting 10 IU/g of human chorionic gonadotropin and inseminated by wet method in the laboratory. The fertilized eggs were 1.12±0.03 mm (1.10~1.16 mm, n=30) in diameter. The embryo began to hatch about 49 hrs after fertilization under water temperature of 23±1℃. The newly-hatched larvae (Yolksac larva) were 3.7±0.1 mm (3.4~3.8 mm, n=16) in total length, and they haven't Melanophore. 5 days after hatching, the Preflexion larva were 5.3±0.2 mm (5.0~5.5 mm, n=16) in total length, and they began to eat a Rotifer. 19 days after hathing, the Flexion larva were 6.0±0.3 mm (5.4~6.5 mm, n=16) in total length, and they began to eat a Brine shrimp. 29 days after hatching, the Postflexion larva were 9.6±0.5 mm (8.3~10.5 mm, n=16) in total length, and dorsal fin rays are were formed. 44 days after hatching, the juvenile were 15.5±1.0 mm (13.5~17.0 mm, n=16) in total length, and all their fin-rays were formed.

• Journal of Practical Agriculture & Fisheries Research
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• v.23 no.1
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• pp.13-26
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• 2021

This study was conducted to identify various types of activities of payment contract for ecosystem services. As supporting services, 12 types of activities were derived: fallow, eco-friendly crop cultivation, shelter creation management, etc. As regulating services, 5 types of activities were derived: stream environment purification, creation and management of riparian vegetation, creation and management of forests for responding to climate change, etc. As cultural services, five types of activities were derived: creation and management of landscape forests, creation and management of ecological trails, managing ecosystem conservation, etc.

• Ecology and Resilient Infrastructure
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• v.9 no.2
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• pp.93-99
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• 2022

It was confirmed that the fish diversity decreased with increasing index of weir's density (IWD) in the four river systems. The IWD showed difference with watershed, it was high in the Nakdong River (NDR). Both two river systems of Gum River (GUR) and Yeongsan River (YSR) were similar, whereas relatively lower density observed in the Han River (HNR) system. A result of 2-Dimensional Kolmogorov-Smirnov (2-DKS) as a nonparametic test showed different threshold values affecting fish diversity with the river systems. The p-values based on D_max, were significantly different at 0.05 level (except for YSR). The threshold values affecting fish diversity were also different with watershed. The values were 1.6/km of the HNR, 1.3/km of the NDR, and 2.3/km of the GUR, respectively. The fish diversity was decreased when IWD is over threshold values. The IWD of total 404 rivers (about 33%) among 1,217 surveyed in this study showed above threshold value. These rivers should be considered first for evaluating river continuity. The IWD and threshold value suggested in this study would be useful for selecting a stream priority for river connectivity study.

• Journal of Korea Entertainment Industry Association
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• v.15 no.1
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• pp.63-73
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• 2021

This study aims to analyze music of Yoon-sang, as a part of musical research, which is the most fundamental approach among academic studies on Korean popular music. Yoon-Sang is a representative composer, who has gone through the 1980s to the present. The result of analysis of 21 songs created by Yoon-Sang showed that his songs are mostly characterized by tonal music, in which chord relationships develop focusing on keynotes. The reason why his music does not sound uniform pursuing stability is he properly added the progression of chromatic chords, based on diatonic chords and melodies. Dominant 7th chord and diminished 7th chord are used the most among diverse techniques adding chromatic colors. Along with these chords, chromatic intervals are used not only in chord progression but also in melodies. The successive, ascending or descending movement of the base line is his common composition and arrangement technique revealed in every song. One of formal changes with the stream of the times is that the number of measured in the pre-chorus and interlude that were of great importance in his songs of the 1990s decreased over time. With regard to harmonic changes, whereas modulation between parts was applied to his 2 songs created in the 2010s. Yoon-Sang's music had one strong tonality overall, but his music began to have more than two tonalities starting the 2010s, and this is a big variation in his music.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.42 no.5
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• pp.627-637
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• 2022

To know the magnitudes of extreme floods for various sizes of watersheds, massive streamflow data is fundamentally required. However, small/medium-size watersheds missed streamflow data because of the lack of gauge stations. In this study, the Streamflow Propagation Method (SPM) was applied to generate streamflow data for small/medium size watersheds with no measurements. Based on the generated streamflow data for ungauged watersheds at three different locations (i.e., Chungju Dam (CJD), Seomjin Dam (SJD), and Andong Dam (ADD) watersheds), the scale ranges of extreme floods were evaluated for different sizes of ungauged watersheds by using the specific flood distribution analysis. As a general result, a range of specific floods decreases with increasing watershed size. The distribution of the specific flood in the same size of a watershed possibly depends on the size and topography of the watershed area. The delivered equations were compared to show the relations between the specific flood and sizes of watersheds. In the comparisons of equations, the Creager envelope curve has the higher potential to represent the maximum flood distribution for each watershed. For the generalization of the maximum flood distribution for three watersheds, optimized envelop curves are obtained with lower RMSE than that of Creager envelope curve.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.42 no.5
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• pp.617-626
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• 2022

In Korea, annual precipitation and its variability have gradually increased since modern meteorological observations began, and the risk of disasters has also been increasing due to significant regional variations and recent abnormal climate conditions. Given that damage from storms and floods mainly occurs around rivers, it is crucial to determine the appropriate design frequency for river-related projects. This study examined existing design practices used to determine hydrological design frequencies and suggested a new method to determine appropriate design frequencies. The study collected available data pertaining to seven evaluation factors, specifically the basin areas, shape parameters, channel slopes, stream orders, backwater effect reaches, extreme rainfall frequencies, and urbanized flood inundation areasfor 413 local rivers in Chungcheongnam-do in Korea. The estimated weights for areas of extreme rainfall frequencies and urbanized flood inundation were found to be 18, having a great effect on determining the design frequency. Compared with the established design frequency in previous government reports, the estimated design frequency increased for 255 rivers and decreased for 158 rivers.

• Journal of Korea Water Resources Association
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• v.54 no.7
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• pp.495-507
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• 2021

With the recent industrial development, accidental pollution in riverine environments has frequently occurred. It is thus necessary to simulate pollutant transport and dispersion using water quality models for predicting pollutant residence times. In this study, we conducted a field experiment in a meandering reach of the Sum River, South Korea, to validate the field applicability and prediction accuracy of RAMS+ (River Analysis and Modeling System+), which is a two-dimensional (2D) stream flow/water quality analysis program. As a result of the simulation, the flow analysis model HDM-2Di and the water quality analysis model CTM-2D-TX accurately simulated the 2D flow characteristics, and transport and mixing behaviors of the pollutant tracer, respectively. In particular, CTM-2D-TX adequately reproduced the elongation of the pollutant cloud, caused by the storage effect associated with local low-velocity zones. Furthermore, the transport model effectively simulated the secondary flow-driven lateral mixing at the meander bend via 2D dispersion coefficients. We calculated the residence time for the critical concentration, and it was elucidated that the calculated residence times are spatially heterogeneous, even in the channel-width direction. The findings of this study suggest that the 2D water quality model could be the accidental pollution analysis tool more efficient and accurate than one-dimensional models, which cannot produce the 2D information such as the 2D residence time distribution.