• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.5
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• pp.502-508
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• 2021

Predicting the settlement of soft ground is an important aspect of soft ground design. In this study, a method is proposed that increases the reliability of settlement predictions based on-site investigation data, including piezocone penetration test results, at the Gimhae-Jinyoung district, adjacent area to the Nakdong River. Soils in the area waweres classified using the Robertson Chart (1986, 1990), and theoretical settlement was calculated using the equations proposed by Terzaghi (1925) and Sanglerat (1972). SPSS was used to obtain the correlation between theoretical and measured settlements. Results produced settlement prediction errors for the Terzaghi and Sanglerat methods of 17.28% and 26.96%, respectively. A correction factor calculated by SPSS correlation analysis for the relation between and theoretical and measured settlements is proposed that improves the reliability of settlement prediction in soils of the classification examined.

• Korean Journal of Ichthyology
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• v.33 no.2
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• pp.57-63
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• 2021

This study was carried out to clarify the egg, larvae and juveniles development of Carassius cuvieri in Nakdong River, Gyeongbuk. The amount of spawning of female C. cuvieri was about 30,400~44,900 (average 37,650±7,250). The egg shape was circular and the size was 1.24~1.37 mm (average 1.31±0.04 mm, n=30). At 100 hours after fertilization, more than of the total embryos were hatched. The newly hatched larvae had an 4.69~5.65 mm in total length (average 5.15±0.31 mm, n=10) and had egg yolk in the abdomen. At 3 days after hatching, the preflexion larvae absorbed all egg yolk was 6.27~6.70 mm in total length (average 6.59±0.08 mm, n=10). On the 10 days after hatching, the postflexion larvae were 8.71~8.92 mm in total length (average 8.81±0.07 mm, n=10), and the tip of the caudal fin was bent at 45°. On the 42 days after hatching, the total length of 15.1~16.8 mm (average 15.8±0.57 mm, n=10) was transferred to juvenile as the number of fins was (iii17 dorsal fins, iii4 anal fins) reached a constant number of each part.

• Ocean and Polar Research
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• v.44 no.4
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• pp.297-310
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• 2022

To understand the chemical composition of aerosols in the Cheju-Korea Straits and their contribution to the ocean by deposition, aerosol samples were collected on board R/V Eardo from November 1997 to May 1999. The average concentrations of Al, NO₃^-, non-sea-salt (nss)-SO₄^2-, and NH₄⁺ in aerosols were 2.19, 5.59, 6.16 and 2.08 ㎍ m^-3, respectively. The Al concentration in the high yellow dust period was about 100 times higher than that in the non-yellow dust period. The concentration ratio of NO₃^-/nss-SO₄^2- ranged between 0.47 and 1.5, indicating that the aerosols in the Cheju-Korea Straits are under the effects of NO_x and SO_x emitted from China, Korea and Japan. The equivalent concentration ratio of [NH₄⁺]/[nss-SO₄^2-+ NO₃^-] with the average of 0.58±0.29 indicates that nss-SO₄^2- and NO₃^- are not neutralized by NH₄⁺. A high activity concentration of ²¹⁰Pb with 1.13-1.23 mBq m^-3 was observed during the high yellow dust period, indicating that ²¹⁰Pb is easily adsorbed in the yellow dust originating from the continent of Asia. The distribution of ⁷Be and NH₄⁺ concentrations showed a strong negative linear correlation during the low yellow dust period, April 1998. The total mineral dust flux in the Cheju-Korea Straits was estimated to be 1.21×10⁶ tons yr^-1, accounting for about 12% of the annual sediment discharge via the Nakdong River. The combined annual deposition of NH₄⁺ and NO₃^- was 0.103 mole N m^-2 yr^-1 was estimated to support 4% of the annual primary productivity in the East China Sea.

• Journal of Environmental Impact Assessment
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• v.32 no.2
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• pp.112-122
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• 2023

To restore the ecological function of contaminated soil and maximize the ecological services provided by the soil, besides the toxicity orrisk caused by pollutants, the functional aspects of the soil ecosystem should be considered. In this study, a method for evaluating the health of cleaned soil was presented, and the applicability of the proposed evaluation method was examined by applying it to soil treated with washing and landfarming. Productivity, habitat, water retention capacity, nutrient cycling, carbon retention capacity, and buffering capacity were used as soil health evaluation indicators. The results showed that the soil health was not completely recovered after remediation, and even in the case of the washed soil, the health was lower than before remediation. On the other hand, there was no significant change in soil quality due to oil pollution, but soil health deteriorated. Unlike the slightly improved soil quality after landfarming treatment, soil health was not completely restored. Therefore, the results of this study indicate that it is desirable to consider both soil quality and health when evaluating the remediation effect. The soil health evaluation method proposed in this study can be usefully utilized for the sustainable use of cleaned soil and to promote ecosystem services.

• Korean Journal of Ichthyology
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• v.34 no.4
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• pp.244-252
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• 2022

The aim of this study was to investigate the early life history of Squalidus gracilis majimae by observing the development of the eggs and morphology of juvenile fish. Squalidus gracilis majimae used in this study were captured in 2021 June from a tributary flowing into Wicheon, located in Uiseong-gun, Gyeongsangbuk-do. For artificial insemination, ovaprim was injected at 0.5 mL/kg. Egg development occurred 12 h after injection. The size of mature eggs of S. gracilis majimae was 0.80~0.85 mm (0.83±0.01 mm, n=30). Incubation time at 22±1℃ ranged from 62.5 to 69 h. The length of larvae immediately after hatching was 2.39~2.53 mm (2.44±0.04 mm, n=30). On the 18th day after hatching, the larvae had a total length of 8.51~9.84 mm (8.95±0.42 mm, n=30), and the tip of the spine was completely curved. On the 22nd day after hatching, the juvenile fish had a total length of 12.6~13.6 mm (13.0±0.36 mm, n=30), with dorsal fins at iii7 and anal fins at i7. Egg size and hatched larvae size were similar for S. gracilis majimae and S. multimaculatus, and cupulae showed a singularity as it disappeared last among related species.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.269-269
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• 2022

최근 낙동강 하구 기수생태 복원에 있어서 중요한 요소 중 하나는 하굿둑 외해측의 보다 높은 정도를 가지는 조석예보치 산정과 이를 통해 하굿둑 방류량과 해수 유입량을 추정하여 주변 환경 등을 예측할 수 있다. 기수생태 복원이 본격으로 논의가 진행 전인 2016년까지는 하구에서 수km 떨어진 기존 조위관측소(부산 및 가덕도)를 활용하여 하류수위를 예측하여 왔지만 조위 높이와 위상 차이로 인하여 활용이 용이하지 않다. 따라서, 낙동강 하굿둑 인접 외해역에서 조석 영향을 받는 수위관측치를 이용하여 조석조화분해를 통해 조위 예측을 보다 정밀하게 산정하는 것이 필요하다. 연구방법으로는 낙동강 하굿둑 외해역에서 관측된 2016년, 2017년 각각 1년간 10분간격으로 관측자료의 저장상태 및 이상자료 유무를 확인하고, 조석조화분해 프로그램인 TASK2000(Tidal Analysis Software Kit) Package를 이용하여 2016년, 2017년 낙동강 하굿둑 인접 외해역에서 관측된 조위자료를 각각 조석조화분해한 결과로 관측조위와 예측조위 비교하였고, 관측조위와 예측조위를 뺀 성분인 조석잔차성분을 구했다. 조화분해결과, 낙동강 하굿둑 외해역은 일반적인 연안역의 조석과는 달리 하천수의 유출, 배수갑문의 조작, 연안사주지형에 의한 조석변형 등 매우 복잡하고 불규칙적인 특성인 기상성분(기압, 바람 등)에 의한 교란을 고려한다면 예측정확도가 상당부분 확보되는 것으로 나타났다. 또한 장주기 성분과 비선형 조석성분의 크기를 비교해 볼 때 거의 편차가 없이 나타나 조석조화상수를 이용한 예보 가능성을 확인할 수 있었다. 조위검증은 2016년의 1년치의 조석자료를 이용하여 조화분해된 조화상수 63개를 이용하여 2017년의 조석 예보치를 산정하였으며, 이를 2017년의 낙동강 하굿둑 외해역의 조석관측치와 조석예측치를 1대 1 비교하는 방식으로 검증하였고, 이들의 상관관계를 파악하기 위하여 두 성분에 대하여 Regression Analysis를 수행하여 예측조위와 관측조위 사이에는 Pre=0.9535×Obs+0.396과 같은 관계식이 성립하는 것으로 분석되었다. 또한, 두 성분간의 상관도는 0.9535로 높게 나타났다. 조위예측 프로그램인 TASK2000 Package 중 MARIE를 이용한 조위예측 프로그램의 신뢰도가 매우 높은 것으로 판단되고, 해당년도 조위예측 시에는 가능하면 직전년도의 1년 조석관측자료를 조화분해하고 얻어진 조화상수를 이용하여 조위예측을 실시하면 보다 정확한 자료를 얻을 수 있다.

• Journal of Korea Water Resources Association
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• v.56 no.11
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• pp.801-813
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• 2023

Recently, as studies about Artificial Neural Network (ANN) are actively progressing, studies for predicting water quality of rivers using ANN are being conducted. However, it is difficult to analyze the operation process inside ANN, because ANN is form of Black-box. Although eXplainable Artificial Intelligence (XAI) is used to analyze the computational process of ANN, research using XAI technology in the field of water resources is insufficient. This study analyzed Multi Layer Perceptron (MLP) to predict Water Temperature (WT), Dissolved Oxygen (DO), hydrogen ion concentration (pH) and Chlorophyll-a (Chl-a) at the Dasan water quality observatory in the Nakdong river using Layer-wise Relevance Propagation (LRP) among XAI technologies. The MLP that learned water quality was analyzed using LRP to select the optimal input data to predict water quality, and the prediction results of the MLP learned using the optimal input data were analyzed. As a result of selecting the optimal input data using LRP, the prediction accuracy of MLP, which learned the input data except daily precipitation in the surrounding area, was the highest. Looking at the analysis of MLP's DO prediction results, it was analyzed that the pH and DO a had large influence at the highest point, and the effect of WT was large at the lowest point.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.14 no.1
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• pp.56-62
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• 2009

Stable carbon isotope analysis was used to investigate the autotrophic carbon sources supporting fisheries in three coastal bay systems of the southern coast of Korea. Carbon isotope ratios (${\delta}^{13}C$) of 31 fish species were analysed and compared with those of a range of potential primary food sources [e.g., seagrass (Zostera marina), seagrass epiphytes, benthic microalgae, macroalgae, marine particulate organic matter (marine POM), marsh plant (Phragmites australis) and terrestrial POM]. ${\delta}^{13}C$ values (range, -16.2${\sim}$-8.3‰) of fishes from the coastal embayment systems were overlapped with those of seagrass (-8.3${\pm}$1.9‰), seagrass epiphytes (-12.4${\pm}$0.6‰), benthic microalgae (-15.4${\pm}$1.6‰) and macroalgae (-16.0${\pm}$1.8‰). In addition, fishes (-12.9${\pm}$1.5‰) from the study area had distinctly higher ${\delta}^{13}C$ values compared to those collected in offshore sites (-17.3${\pm}$0.8‰) of the southern sea of Korea and Nakdong River (-23.2${\pm}$1.6‰). This result indicates that carbon supporting fish communities of these coastal bay systems is mainly derived from the local benthic producers.

• Journal of the Korean Geosynthetics Society
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• v.23 no.1
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• pp.39-47
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• 2024

In this study, physical property tests and standard consolidation tests were conducted on the marine clay of Busan New Port and North Port, the middle and lower reaches of the Nakdong River including Gimhae and Yangsan, and Ulsan regions. The moisture content, a property unrelated to sample disturbance with small individual test errors, was used for regression analysis with the compression index, virgin compression index, consolidation coefficient, expansion index, and secondary compression index, among others. Subsequently, the correlation and accuracy were evaluated. Upon analyzing the correlation between the moisture content, void ratio, and liquid limit commonly used physical properties for calculating compression indexes, it was confirmed that the liquid limit had the lowest correlation. Through a linear regression analysis of the consolidation constants using the current moisture content in the natural state, a high correlation was demonstrated. Relationship equations were then presented to determine settlement and settlement time. This study suggests that moisture content can be utilized as an alternative for evaluating and calculating consolidation constants when examining ground settlement in sedimentary clays distributed in the Busan and Gyeongnam regions.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.6
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• pp.2211-2221
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• 2013

During the four river restoration project, several weirs were constructed in the four rivers to prevent drought and flood, to improve water quality, and to manage water resources. However, due to the weir construction, bed changes are produced in the upstream channel of installed weirs because the incoming flow velocity is reduced and sediment transport capacity is also lowered. Especially, since the Haman Weir is located in the lowest downstream section among newly installed weirs in Nakdong River, bed change and sedimentation problems are expected due to the mild slope and reduced velocity. Therefore, numerical simulation was performed to analyze flow and bed changes in the upstream channel of Haman Weir and to evaluate quantitatively sediment control methods for bed stabilization using CCHE2D model. As a result of flow and bed change simulation after installation of Haman Weir, the flow velocity at the initial condition was faster than the final bed condition with the specific simulation time and it was represented that the locations where bed changes were great were identical for all modeling conditions of flow discharge. In case of 4.5 m of water level lowered from 5.0 m of the management water level at Haman Weir for bed stabilization, the flow velocity was generally faster than the case of the management water level and the continuous erosion was developed at the most narrow channel section as the applied discharge and simulation period were increased. The channel width extension at the most narrow channel section was proposed in this study to prevent and stabilize continuos bed erosion. As a result of numerical analysis, there was no bed erosion after channel width extension and it was presented that the channel geometry extension was effective for bed stabilization at Haman Weir.