• 한국환경과학회지
• /
• 제19권7호
• /
• pp.843-848
• /
• 2010

This study focused on the characteristics of change soil water with respect to soil thickness and soil mixture ratio, in order to effectively carry out an afforestation system for a roof with a low level of management and a light weight. Soil hardness tended to increase as sand particle was increase regardless soil thickness and soil porosity had more higher artificial soil than natural soil mixture. In case of soil pH, natural soil mixture had between 6.7 and 7.4, and artificial soil mixture had 6.0~6.8. Organic matter, electrical conductance and exchangeable content were highest in $L_{10}$, which it had the highest leafmold ratio. Soil moisture tension(kPa) in 15cm soil thickness was observed natural soil mixture had a considerable change but artificial soil mixture had a gradual change when non-rainfall kept on. In the experimental $L_{10}$, $S_{10}$, $S_7L_3$ and $S_5L_5$ object, the amount of moisture tended to rapidly decrease. However, in the experimental $P_7P_1L_2$, $P_6P_2L_2$, $P_5P_3L_2$ and $P_4P_4L_2$ objects, which contained pearlite and peat moss, the amount of moisture tended to gradually decrease. As a result, the use of a artificial soil mixture soil seems to be required for the afforestation of a roof for a low level of management.

• 한국기후변화학회지
• /
• 제8권2호
• /
• pp.109-123
• /
• 2017

The effects of recent climate change on hydrological systems could affect the Winter Olympic Games (WOG) because the event is dependent on suitable snow and ice conditions to support elite-level competitions. We investigate the long-term variability and change in winter total precipitation (P), snowfall water equivalent (SFE), and ratios of SFE to P during the period 1973/74~2015/16 in Gangwon province. The climatological percentages of SFE relative to winter total precipitation were 71%, 28%, and 44% in Daegwallyeong, Chuncheon, and Gangneung, respectively. The winter total P, SFE, and SFE/P has decreased (but not significantly), although significant increases of winter maximum and minimum temperature were detected at a 95% confidence level. Notably, a significant negative trend of SFE/P at Daegwallyeong in February, the month of the WOG, was attributable to a larger decrease in SFE related to the increases in maximum and minimum temperature. Winter wet-day minimum temperatures were warmer than climatological minimum temperatures averaged over the study period. The 20-year return values of daily maximum P and SFE decreased in Yongdong area. Since the SFE/P decrease with increasing temperature, the probability of rainfall rather than snowfall can increase if global warming continues.

• 대한한의학방제학회지
• /
• 제10권2호
• /
• pp.97-112
• /
• 2002

In order to investigate the effect of Sagoonja-Tang, Samool-Tang and Yookmijihwang-Tang against the cold, heat and immobilization stress, each formula was injected intragastically to mice exposed to forced cold water swimming($4^{\circ}C$), forced hot water swimming($42^{\circ}C$) and immobilization stress before measuring the change of plasma corticosterone level of mice. The results were as follows: 1. One hour after each Sagoonja-Tang, Samool-Tang, Yookmijihwang-Tang with the dose of 1g／kg, 3g／kg each were administered to mice, we put cold stress($4^{\circ}C$) on mice for 3min. Then those prescriptions didn't show any significant effect on plasma corticosterone level. however, Yookmijihwang-Tang(1g/kg) showed a significant increase(p〈0.05), and Samool-Tang(3g/kg) showed a small increase. 2. One hour after Samool-Tang, Sagoonja-Tang and Yookmijihwang-Tang with the dose of 1g／kg, 3g／kg each were administerd, mice exposed to heat stress($42^{\circ}C$) for 3 min. Samool-Tang(1g/kg) and Yookmijihwang-Tang(lg/kg) showed significant decrease of corticosterone level(p〈0.01, p〈0.05) but Sagoonja-Tang didn't change it. In the case of the dose of 3g/kg, only Samool-Tang decreased corticosterone level(P〈0.01), but Sagoonja-Tang, Yookmijihwang-Tang didn't make significant effect on plasma corticosterone level of the mice exposed to heat stress($42^{\circ}C$ ). 3. Those mice which exposed to immobilization stress one hour after Sagoonja-Tang, Samool-Tang, Yookmijihwang-Tang with the dose of 1g/kg and 3g/kg didn't show effective decrease of corticosterone level. However, Sagoonja-Tang(3g/kg), Samool-Tang(lg/kg, 3g/kg) showed the effect of mild increase of corticosterone level rather than decrease. These data revealed that the effect-variation of prescriptions depended on the kinds of stress and the dose of prescriptions had a different effect on therapy.

• Geomechanics and Engineering
• /
• 제24권6호
• /
• pp.531-543
• /
• 2021

Freezing and thawing of pore water within backfill can affect the stability of retaining wall as the phase change of pore water causes changes in the mechanical characteristics of backfill material. In this study, the effects of freezing and thawing on the mechanical performance of retaining wall with granular backfill were investigated for various temperature and groundwater level (GWL) conditions. The thermal and mechanical finite element analyses were performed by assigning the coefficient of lateral earth pressure according to phase change of soil for at-rest, active and passive stress states. For the at-rest condition, the mobilized lateral stress and overturning moment changed markedly during freezing and thawing. Active-state displacements for the thawed condition were larger than for the unfrozen condition whereas the effect of freezing and thawing was small for the passive condition. GWL affected significantly the lateral force and overturning moment (Mo) acting on the wall during freezing and thawing, indicating that the reduction of safety margin and wall collapse due to freezing and thawing can occur in sudden, unexpected patterns. The beneficial effect of an insulation layer between the retaining wall and the backfill in reducing the heat conduction from the wall face was also investigated and presented.

• 한국해안·해양공학회논문집
• /
• 제29권5호
• /
• pp.228-238
• /
• 2017

우리나라 연안해역에서 조사된 조위 조화상수를 수집하여 조석 분포와 비선형 조석특성의 분포를 조사하고, 국립해양조사원에서 관측한 목포항과 군산외항의 조위자료를 조화분석하여 비선형 조석의 경년변화와 비조화상수(고조위, 저조위, 조차)의 경년변화의 관련성을 검토하였다. 비선형 조석의 발생과 조석형태수가 관련성이 있음을 확인할 수 있었으며, 비선형 분조의 변화는 고조위와 저조위의 변화에 큰 영향을 주었다. 목포항에서는 해안개발로 인해서 비선형 분조의 진폭과 위상이 크게 변화하고, 이로 인해서 고조위가 상승하고, 저조위는 하강하여 조차가 증가하였다. 군산외항에서는 새만금방조제 준공이후에 비선형 조석의 영향으로 고조위는 하강하고, 저조위는 상승하여 조차가 감소하였다.

• 한국전자통신학회논문지
• /
• 제16권2호
• /
• pp.371-378
• /
• 2021

본 연구에서는 한국 남동해역에 발생하는 냉수대의 공간적인 분포를 구분하기 위해 2016 ~ 2018년의 고리, 양포의 해양 관측 부이 수온자료와 GHTSST Level 4 재분석 해수면 온도자료를 K-means clustering 기법을 활용하여 분석하였다. 부이자료는 남동해역에서 고리와 양포 지점의 수온변화 및 냉수대 발생을 파악하기 위해 활용하였다. 그 결과 냉수대 발생 시점에 고리와 양포의 수온이 동일하게 감소하였다. 이에 냉수대 발생시 SST의 변화를 보기 위해 수온의 역수와 SST의 분산을 비교하였다. 수온이 변화하는 시점에 SST의 분산도 증가하는 것을 나타내었는데 이를 통해 냉수대 발생시 해역의 SST의 수온분포에 변화가 있다는 것을 알 수 있었다. 냉수대 발생해역을 분류하기 위해 K-means clustering을 활용하였다. Elbow 기법을 활용하여 분류를 위한 최적의 K값을 찾아낸 후 분류를 진행한 결과 연안의 차가운 해수가 존재하는 지역을 찾아낼 수 있었다. 이를 통해 냉수대 발생해역의 공간적인 분포 및 확산범위를 추정하여 향후 냉수대로 인한 피해 파악 및 공간적인 확산 예측연구에 활용할 수 있을 것이라 판단된다.

• 한국지하수토양환경학회:학술대회논문집
• /
• 한국지하수토양환경학회 2003년도 추계학술발표회
• /
• pp.515-518
• /
• 2003

Groundwater recharge rate can be estimated from groundwater head rebound due to rainfall. Groundwater level changes are monitored for 10 months at Yugu area. Difference between two recharge rates calculated by rainfall and by effective rainfall is 1.1%~1.6%. Since this method ignores soil water percolation during groundwater level regression, the actual recharge rate may be higher than estimated one by cumulative rainfall and groundwater level change.

• 한국수자원학회:학술대회논문집
• /
• 한국수자원학회 2023년도 학술발표회
• /
• pp.48-48
• /
• 2023

The intensified droughts under climate change are expected to threaten stable water resource availability. Droughts exceeding the magnitude of historical variability could occur increasingly frequently under future climate conditions. It is crucial to understand how drought will evolve over time because the assumption of hydrological stationarity of the past decades would be inappropriate for future water resources management. However, the timing of the emergence of unprecedented drought conditions under climate change has rarely been examined. Here, using multimodel hydrological simulations, we investigate the changes in the frequency of hydrological drought (defined as abnormally low river discharge) under high and low greenhouse gas concentration scenarios and with existing water resources management and estimate the timing of the first emergence of unprecedented regional drought conditions that persist for over several consecutive years. This new metric enables a new quantification of the urgency of adaptation and mitigation with regard to drought under climate change. The times are detected for several sub-continental-scale regions, and three regions, namely, southwestern South America, Mediterranean Europe, and northern Africa, exhibit particularly robust and earlier critical times under the high-emission scenario. These three regions are expected to confront unprecedented conditions within the next 30 years with a high likelihood, regardless of the emission scenarios. In addition, the results obtained herein demonstrate the benefits of the lower-emission pathway in reducing the likelihood of emergence. The Paris Agreement goals are shown to be effective in reducing the likelihood to the unlikely level in most regions. Nevertheless, appropriate and prior adaptation measures are considered indispensable to when facing unprecedented drought conditions. The results of this study underscore the importance of improving drought preparedness within the considered time horizons.

• 수산해양기술연구
• /
• 제59권4호
• /
• pp.315-327
• /
• 2023

In the last five decades, there has been a consistent decline in the total catch of fisheries in the Korean jurisdiction since the peak in 1986. The decline in catch slowed and slightly rebounded in the 2000s, but changed back to a decline in the 2010s. As indicators that can identify changes in the marine ecosystem, trophic level (TL), biodiversity index (H'), and the ratio between pelagic fish and demersal fish (P/D) were analyzed by each local marine ecosystem. There were some different changes in each local marine ecosystem, but the mean TL and H' decreased and P/D increased in general in Korean waters. Demersal fish, which were dominant in the 1970s and 1980s, declined, and small pelagic fish and cephalopods have dominantly changed since the 1990s. However, these changes are not simple, and they are fluctuating in complex ways relating to each marine ecosystem and the timing. It is believed that changes in marine ecosystems in Korean waters are likely caused by a combination of fisheries and climate change. The ecosystem indicators reflected a change in the total catch, a sharp drop in catch of demersal fish, and increasing catch of pelagic fish since the mid-1980s.

• 대한원격탐사학회:학술대회논문집
• /
• 대한원격탐사학회 2004년도 Proceedings of ISRS 2004
• /
• pp.566-569
• /
• 2004

This study is to trace the change of stream shape using the past series of aerial photographs, and to compare the land use changes of riparian area along the stream. For the Gyeongan national stream, aerial photographs of 1966, 1981 and 2000 were selected and ortho photographs were made with interior orientation and exterior orientation, respectively. As apparent changes of the stream, the consolidated reaches of stream with levee construction were straightened and their stream widths were widened. Especially the stream width of inlet part of Paldang lake was widened almost twice because of the rise of water level by dam construction in 1974. The land use maps (1966, 1981,2000) of riparian areas were also made, respectively and classified into 6 categories (water, forest, agricultural land, urban area, road, sandbar) by digitizing. The area of forest and agricultural land decreased and urban area increased as the stream maintenance was performed.