• Proceedings of the Korea Water Resources Association Conference
• /
• 2023.05a
• /
• pp.192-192
• /
• 2023

우량계는 강우 자료를 수집하는 전통적인 방법 중 하나로, 연속적이고 직접적인 설치가 가능하다. 하지만 지형적 특성에 영향을 받아 강우량을 과소 측정하는 문제점이 있다. 이러한 문제를 해결하기 위해 국지적인 호우, 강우 이동 및 강우 상황 등을 파악할 수 있는 레이더를 이용한 강우 측정이 활용된다. 하지만 레이더 기반 측정 또한 우량계와 마찬가지로 과소 측정하는 문제점이 있다. 측정 한계를 극복하기 위해 최근에는 위성 기반 강우 자료를 사용하고 있다. 위성 기반의 강우 자료는 측정이 어려운 장소에서도 강우량의 수집이 가능하며, 지표 변화를 관측하여 강우 측정의 정확도를 높일 수 있다. 고화질 위성 자료인 CHIRPS (Climate Hazards Group InfraRed Precipitation with Stations) 자료는 미국 국제개발처, 항공우주국, 해양 대기청의 지원으로 1980년부터 현재까지 전 지구적 (50°S-50°N, 180°E-180°W) 0.05° × 0.05°의 해상도를 가진 강우량 데이터를 개발하였다. 본 연구에서는 전국 54개 ASOS (Automated Synpotic Observing System)에서 관측한 월 단위 및 일 단위 강우 자료를 기준으로 CHIRPS 강우 자료를 비교하였다. 또한, 다른 위성 강우 자료들 (APHRODITE (Asian Precipitation Highly Resolved Observation Data Integration Towards Evaluation), CMORPH (Climate Prediction Cneter morphing method))과도 비교하여 국내 적용성을 확인하였다. 강우 자료의 정확도를 비교하기 위해서 Box-plot, RMSE (Root Mean Squared Error) 등을 산정하였으며, 강우 발생 일을 비교하고자 오차 행렬을 활용하였다. 비교 결과를 통해서 CHIRPS 강우 자료가 다른 위성 강우 자료들에 비해서 국내 적용성이 높은 것을 확인할 수 있었으며, 추후 국내 수문학 연구에서 기초자료로서 활용될 수 있을 것으로 판단된다.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2023.05a
• /
• pp.115-115
• /
• 2023

최근 기후변화의 영향으로 국내에서 강우량과 유출량의 변동성이 커짐에 따라 효율적으로 수자원을 관리하는 데 어려움을 겪고 있다. 따라서 수자원 관리 측면에서 강우관측소를 대상으로 군집 분석과 경향성 분석을 통해 사전에 강우 시계열 자료의 추세와 특징을 파악하면 용수 공급과 가뭄 및 홍수피해 저감 등에 효과적으로 대처할 수 있다. 본 연구에서는 2000년부터 2019년까지낙동강 유역의 64개 강우관측소를 대상으로 동질성 검정과 수정 Mann-Kendall (MK) 검정을 적용하여 강우 시계열 자료의 월별, 계절별, 연도별 경향성 분석을 수행하였다. 또한, 경향성이 나타나는 관측소별 세부지표(연평균 강우량, 표고 등)를 기준으로 K-means 군집 분석을 수행하여 군집별 강우 특성을 파악하고자 하였다. 분석을 수행한 결과 경향성 분석에선 3월, 4월, 11월, 12월, 봄 및 가을에는 강우량이 증가 추세를 보였고 1월, 5~9월, 여름과 연도별로는 감소 추세가 나타났다. 또한 군집 분석에서는 Silhouette analysis를 기반으로 최적의 군집 개수를 3개로 설정했을 때 군집별 강우 세부지표의 통계값이 관측소별 표고에 비례하는 특징이 나타났다. 연구를 통해 도출된 군집별 강우 특성과 관측소별 경향성 분석결과를 연계하면 강우량의 변동성을 고려한 효율적인 수자원 관리 방안을 마련하는 데 활용할 수 있을 것으로 판단된다.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2021.06a
• /
• pp.184-184
• /
• 2021

2020년의 경우 대기 상층 제트기류가 크게 강화됨에 따라 작은 규모의 저기압의 발달이 평년보다 두 배 이상 증가하였고, 그로 인해 장마가 최대 54일가량 지속되며 1조 371억 원 가량의 대규모 침수피해가 발생하였다. 이와 같이 최근 기후변화로 인한 이상 기후가 빈번하게 발생하고 있으며, 그로 인해 홍수, 태풍과 같은 재난의 강도 및 파급되는 재산피해가 점차 증가하고 있는 추세이다. 따라서 본 연구에서는 기후변화를 고려하여 향후 30년간 강우량 변화 추이를 파악하고, 이에 따라 파급되는 재난피해 규모의 증가 추세를 확인하고자 하였다. 기후변화 시나리오는 IPCC AR6(Intergovernmental Panel on Climate Change - Sixth Assessment Report)에서 제시하고 있는 시나리오 중 극한 시나리오인 SSP5-8.5와 안정화 시나리오인 SSP2-4.5 시나리오를 활용하고자 하였다. GCM(General Circulation Model) 자료는 전 지구적 모형으로 공간적 해상도가 낮은 문제가 있기 때문에, 국내 적용을 위해서는 축소기법을 적용해야 한다. 본 연구에서는 공간적 축소를 위해 통계학적 기법 중 인공지능 기법을 적용하고 Reference data와 종관기상관측(ASOS)의 실측 강우 자료(1905 ~ 2014년)를 통해 학습된 모형의 정확도 검증을 수행하였다. 또한 연 강수량과 연도별 홍수피해의 규모 및 빈도를 확인하여 연도별 강수량 증가에 따른 피해 규모의 증가를 관계식을 도출하였다. 이후 최종적인 축소기법으로 모형을 통해 향후 2050년까지 부산광역시의 예측 강우량을 전망하여 연 강수량의 증가량과 피해 규모의 증가량을 전망해보고자 하였다. 본 연구 결과는 부산광역시의 예방단계 재난관리의 일환으로 적응형 기후변화 대책 수립에 기초 자료로써 활용될 수 있을 것이다.

• Membrane Journal
• /
• v.34 no.2
• /
• pp.114-123
• /
• 2024

Hydrogen isotopes can be categorized into light hydrogen, heavy hydrogen, and tritium based on the number of neutrons, each of which is used in specific fields. Specifically, deuterium is of interest in the electronics industry, nuclear energy industry, analytical technology industry, pharmaceutical industry, and telecommunications industry. Conventional methods such as cold distillation, thermal cycling absorption processes, Girdler sulfide processes, and water electrolysis have their own advantages and disadvantages, leading to the need for alternative technologies with high separation and energy efficiency. In this context, membrane-based hydrogen isotope separation is one of the promising solutions to reduce energy consumption. In this review, we will present the state-of-the-art in hydrogen isotope separation using membranes and their operating principles. The technology for separating hydrogen isotopes using membranes is just beginning to be conceptualized, and many challenges remain to be overcome. However, if achieved, the economic benefits are expected to be significant. We will discuss future research directions for this purpose.

• Korean Journal of Soil Science and Fertilizer
• /
• v.32 no.1
• /
• pp.12-21
• /
• 1999

This study was carried out to improve the cultivation method of paddy rice when the application amount of nitrogen decreased. We investigated the growth and the yield of paddy rice, the changes of nutrients in the soil solution, soil and paddy rice. The results are as follows. The yield at the N4 plot(N $73kg\;ha^{-1}$) was higher than that of control(N $110kg\;ha^{-1}$). N1(N $55kg\;ha^{-1}$), N2(N $55kg\;ha^{-1}$), and N3(N $73kg\;ha^{-1}$). The number of panicle per square meter at the N4 plot was larger than that of control plot. The increase in yield at the N4 plot was due to increased number of panicle where planting density was two times higher compared to the control plot. The availability of nitrogen at the N4 plot also was two times higher than that of control plot. The pH in soil solution was around 7 and did not change largely. The $K^+$ concentration in soil solution at all plots decreased gradually. The $Ca^{2+}$ concentration in soil solutions increased gradually, and decreased at the later stage slightly. The P concentration in soil solution decreased gradually, increased after the heading stage, and then decreased due to decrease of soil temperature. Leaching of $Ca^{2+}$ was higher, while that of $K^+$ and P was lower compared to other ions. Total content of nutrients in soil after harvest decreased. Contents of total N, total P, and O.M. at the N4 plot were higher than those of the other plots. The content of total N and O.M. was correlated to yield. Contents of N, P and K in rice straw and grain at the N4 plot were the highest among all plots. In conclusion, to decrease N application amount in paddy rice cultivation as well as to maintain yield, planting density should be twice of control and the amount of application of N fertilizer should be two-third of control where N fertilizer should be applied mainly at 20 and 10 day before heading.

• Journal of The Korean Society of Grassland and Forage Science
• /
• v.18 no.3
• /
• pp.179-186
• /
• 1998

This experiment was conducted to study on forage utility of Diplachne fusca L. which live in reclaimed saline land of midwest region of Korea The secondary experiment was conducted to know on growth characteristics, forage yield and forage value of Diplachne fusca L. in order to get a necessary data on possible utilization of native plant as a forage crop and practical use of reclaimed saline land. The results obtained are summarized as follows; 1. The growth of Diplachne fusca L. was neary finished at heading stage. So plant height, leaf length, leaf width, stem diameter, tillering number, fresh weight and dry weight per plant were 137.5cm, 42.6cm, 4.65mm, 2.48mm, 15.3 tiller, 44.68 and 15.3g respectively. 2. Fresh weight was the highest with 4,460kg/10a at heading stage, dry weight was 1,530kg/10a at heading stage and 1,630kg/10a at 20 day after heading. The fresh weight was significantly difference between cutting height level according to cutting time, but total fresh weight was not significantly difference between cutting height level. Total dry weight was significantly difference between cutting height, so it was a large yield at cutting height of 10cm. 3. The contents of crude protein, available protein, digestible protein and TDN were the range of 12.3~3.7%, 12.3~3.7% 10.8~3.6% and 65.2~60.7% according to growth stage, respectively. The highest yield of crude protein, available protein, and digestible protein were showed at heading stage, that of TDN showed at 20 day after heading. The contents of ADF and NDF were the range of 36.4~50.0% and 62.7-80.5% according to growth stage. 4. The contents of P, Ca, K and Mg were the range of 0.31~0.20, 0.70~0.52, 1.74~1.28 and 0.19~0.18% according to growth stage, respectively. The highest yield of P, Ca and K was showed at heading stage, that of Mg showed at 20 day after heading. 5. The contents of ENE, NEL, NEM and NEG were the range of 1.42~1.29, 0.68~0.62, 0.68~0.61 and 0.40~0.35 McaVlb according to growth stage, respectively. The highest yield of ENE, NEL, NEM and NEG was showed at 20 day after heading by inuease after heading. 6. The grasseating ratio of Diplachne fusca L. of before and after heading by milk cattle was 96.5% and 95.3%, respectively.

• Journal of The Korean Society of Grassland and Forage Science
• /
• v.1 no.1
• /
• pp.18-28
• /
• 1978

To study about the effect of harvested stage and physical treatment such as wilting or chopping of plant material on the quality of silage, Italian ryegrass(Lolium multiflorum) harvested at pre-headed or heading stage and Seombadi(Dystaenia takesimana Nakai) harvested at pre-flowering stage, were used for the purpose. The materials were treated in four different ways which were a) non-treated, b) one day-wilted, c) chopped with 1 to 2cm length and d) wilted and chopped, and those were ensiled in plastic containers and stored at room temperature for three months. After three months of storage, it was investigated and obtained the following results. 1) Having 6.31 of NFE/CP ratio and low content of crude fiber, Seombadi contained more suitable constituents for silage than Italian ryegrass. 2) Under the non-treated or chopped condition, the loss of NFE was higher, and lower with wilted material. 3) Wilting or chopping improved DM digestibility. 4) Compared with Italian ryegrass harvested at pre-headed stage, the storage amount per unit volume of heading stage-Italian ryegrass and Seombadi were higher 8% and 69% respectively, and wilting and/or chopping increased the storage amount 41 to 134%. 5) The majority of weight loss during storage was observed at 1st week after ensiling, it continued slightly until 4th week. The highest loss in 8th week were 3.76% of nontreated material. 6) One day wilting increased DM content of silage 23 to 131%. Wilting and chopping increased pH and lactic acid improved the quality considerably. 7) The correlation between $NH_3$ and butyric acid, and between lactic acid and DM were r=0.782**, r=0.634** respectively. The regression equation were y=12.853X+4.908 (X=butyric acid), y=0.016X+1.309(X=DM content), respectively. 8. The above results indicate that it is necessary to wilt or chop material to make good quality silage from Italian ryegrass, and such treatment can improve the quality of silage with Seombadi also.

• Geotechnical Engineering
• /
• v.2 no.1
• /
• pp.27-44
• /
• 1986

The measured soil data are analyzed to the descriptive statistics and classified into the four models of uncorrelated-normal (UNNO), uncorrelated-nonnormal (VNNN), correlatedonnormal(CONN), and correlated-nonnormal(CONN) . This paper presents the comparisons of reliability index and check points using the advanced first-order second-moment method with respect to the four models as well as BASIC Program. A sin91e-mode Performance function is consisted of the basic design variables of bearing capacity and settlements on shallow foundations and input the above analyzed soil informations. The main conclusions obtained in this study are summarized as follows: 1. In the bearing capacity mode, cohesion and bearing-capacity factors by C-U test are accepted for normal and lognormal distribution, respectively, and negatively low correlated to each other. Since the reliability index of the CONN model is the lowest one of the four model, which could be recommended a reliability.based design, whereas the other model might overestimate the geotechnical conditions. 2. In the case of settlements mode, the virgin compression ratio and preccnsolidation pressure are fitted for normal and lognormal distribution, respectively. Constraining settlements to the lower ones computed by deterministic method, The CONN model is the lowest reliability of the four models.

• Clean Technology
• /
• v.26 no.4
• /
• pp.329-335
• /
• 2020

Methanol synthesized from renewable hydrogen and captured CO2 has recently attracted great interest as a sustainable energy carrier for large-scale renewable energy storage. In this study, molten carbonate fuel cell's performance was investigated with the direct conversion of methanol into syngas inside the anode chamber of the cell. The internal reforming of methanol may significantly improve system efficiency since the heat generated from the electrochemical reaction can be used directly for the endothermic reforming reaction. The porous Ni-10 wt%Cr anode was sufficient for the methanol steam reforming reaction under the fuel cell operating condition. The direct supply of methanol into the anode chamber resulted in somewhat lower cell performance, especially at high current density. Recycling of the product gas into the anode gas inlet significantly improved the cell performance. The analysis based on material balance revealed that, with increasing current density and gas recycling ratio, the methanol steam reforming reaction rate likewise increased. A methanol conversion more significant than 90% was achieved with gas recycling. The results showed the feasibility of electricity and syngas co-production using the molten carbonate fuel cell. Further research is needed to optimize the fuel cell operating conditions for simultaneous production of electricity and syngas, considering both material and energy balances in the fuel cell.

• Korean Journal of Mineralogy and Petrology
• /
• v.35 no.3
• /
• pp.313-331
• /
• 2022

Natural or native abiotic molecular hydrogen (H₂) is a major component in natural gas, however yet its importance in the global energy sector's usage as clean and renewable energy is underestimated. Here we review the occurrence and geological settings of native hydrogen to demonstrate the much widesprease H₂ occurrence in nature by comparison with previous estimations. Three main types of source rocks have been identified: (1) ultramafic rocks; (2) cratons comprising iron (Fe²⁺)-rich rocks; and (3) uranium-rich rocks. The rocks are closely associated with Precambrian crystalline basement and serpentinized ultramafic rocks from ophiolite and peridotite either at mid-ocean ridges or within continental margin(Zgonnik, 2020). Inorganic geological processes producing H₂ in the source rocks include (a) the reduction of water during the oxidation of Fe²⁺ in minerals (e.g., olivine), (b) water splitting due to radioactive decay, (c) degassing of magma at low pressure, and (d) the reaction of water with surface radicals during mechanical breaking (e.g., fault) of silicate rocks. Native hydrogen are found as a free gas (51%), fluid inclusions in various rock types (29%), and dissolved gas in underground water (20%) (Zgonnik, 2020). Although research on H₂ has not yet been carried out in Korea, the potential H₂ reservoirs in the Gyeongsang Basin are highly probable based on geological and geochemical characteristics including occurrence of ultramafic rocks, inter-bedded basaltic layers and iron-copper deposits within thick sedimentary basin and igneous activities at an active continental margin during the Permian-Paleogene. The native hydrogen is expected to be clean and renewable energy source in the near future. Therefore it is clear that the origin and exploration of the native hydrogen, not yet been revealed by an integrated studies of rock-fluid interaction studies, are a field of special interest, regardless of the presence of economic native hydrogen reservoirs in Korea.