• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.101-101
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• 2019

전 지구적 기온상승으로 인한 기후변화는 사회적, 수문학적, 다양한 분야에 영향을 미친다. 또한 IPCC(Intergovernmental Panel on Climate Change)의 보고서에 따르면 미래에도 지속적으로 기온상승이 예상되며, 이러한 현상은 인류의 삶에 큰 영향을 미칠것으로 예상된다. 또한 수자원 및 관련 분야에서도 기온 상승에 따른 강수량, 강수의 주기 변동, 극한 기후사상의 심도(severity)와 빈도 변화에 따른 다양한 연구가 진행되고 있으며, 미래의 강우량과 온도를 예측하는 기후변화연구에서는 다양한 기후모형을 고려하여 분석한다. 하지만 모든 기후모형이 우리나라에 적합한 것은 아니므로 과거 기후를 모의한 결과를 토대로 성능이 뛰어난 모형의 결과에 더 높은 가중치를 주고 미래를 예측하는 연구가 활발히 진행되고 있다. 일반적으로 기후모형으로 GCM (General Circulation Model) 모의 결과가 이용되는데 우리나라에 대한 GCM 결과의 정확성을 분석하는 연구는 부족한 실정이다. 따라서 본 연구에서는 21개의 GCM을 대상으로 과거 모의 자료(1970년~2005년)를 실제 관측소에서 관측된 강수량과 비교하여 각 GCM들의 성능을 평가하고 이를 토대로, GCM들의 우선순위를 선정하였다. 또한 격자 기반 GCM 결과를 IDW (Inverse Distance Weighted) 방법을 사용하여 기상관측소로 지역적 상세화를 수행하였으며, GCM과 관측자료 사이의 편이를 보정하기 위해 6가지의 Quantile Mapping 방법과 Random Forest 기법을 사용하였다. 또한 편이 보정 기법 중 성능이 좋은 기법을 선택하여 관측소에 적용하였다. 편이 보정된 GCM 모의결과에 대한 성능을 토대로 우수한 GCM 순위를 도출하기 위해 다기준의사결정기법 중 하나인 TOPSIS (Technique for Order of Preference by Similarity to Ideal Solution)를 이용하였다. 그리고 GCM의 전망기간인 2010년부터 2018년까지의 Machine learning 방법과 Quantile mapping의 기법을 비교 및 성능이 우수한 편이 보정 방법을 선택한 후 전망기간 동안의 GCM 성능의 우선순위를 선정하였다.

• Journal of Navigation and Port Research
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• v.45 no.6
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• pp.314-324
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• 2021

Competition between ports around the world is intensifying to attract transshipment cargo. However, recently, there have been concerns about the departure of transshipment cargo volume at Busan Port, such as the lifting of the cabotage policy in China's shipping sector and the implementation of a safe fare system. In terms of operation, terminal congestion and vehicle waiting time are seriously occurring due to imbalance in the transshipment volume of each terminal and vehicles concentrated in a specific time period. In this paper, we propose a method of inter-terminal transportation (ITT) using buffer space to solve the problem caused by inefficient ITT systems and presented a mixed integer programming (MIP) for the problem. The effect of using the buffer space was analyzed for various work volumes and capacity fluctuation ranges by applying the terminal congestion pattern and ITT vehicle in/out pattern based on the Busan New Port data.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.5
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• pp.487-494
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• 2019

A Small-Sat Power System Design and Development should be depend on space environment such as solar wind with Electromagnetic field by hurdle of techniques. It is surmount solution of trend that will unitize and converge with power module in these days. The level of modularize means that applying Universal Middleware for payload power module requirements. The scope of target system is a main power provider module and operational subunit that can be implemented with the final power module distribution loads to consume for continuous process. A Universal Middleware strengthen to build power module from satellite power system should be accuracy and consuming data. A Power Service Module and dynamic system drive interactive management between power distribution and consumer module by Range Control. Consequently, suggesting evaluation, unexpecting payload system power consumer that makes fine variable resources in the development design process and efficiency.

• Journal of Korean Society of Disaster and Security
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• v.14 no.1
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• pp.41-50
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• 2021

As a method of predicting the displacement of river levee in advance, Differential Interferometry (D-InSAR) kind of InSAR techniques was used to identify weak points in the area of the levee collapes near Gumgok Bridge (Somjin River) in Namwon City, which occurred in the summer of 2020. As a result of analyzing the displacement using five images each in the spring and summer of 2020, the Variation Index (V) of area where the collapse occurred was larger than that of the other areas, so the prognostic sysmptoms was detected. If the levee monitoring system is realized by analyzing the correlations with displacement results and hydrometeorological factors, it will overcome the existing limitations of system and advance ultra-precise, automated river levee maintenance technology and improve national disaster management.

• Korean Journal of Environmental Biology
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• v.39 no.1
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• pp.81-87
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• 2021

The monthly variability in marine algal flora and community structure was examined in the intertidal zones of Doripo, and the biomass of an edible alga, Ulva prolifera, at Gaip-ri of Hampyong Bay on the southwestern coast of Korea was investigated over one year from April 2008 to March 2009. A total of 22 seaweeds were identified including five green, four brown, and 13 red algae. Based on importance value, Ulva australis was dominant over the year and the subdominant species were Ulva linza and Caulacanthus ustulatus at the Doripo coast of Hampyong Bay. The vertical distribution in terms of importance values was in the order of Ulva linza - C. ustulatus - U. australis - Sargassum thunbergii from the upper to the lower intertidal zones. The biomass of U. prolifera ranged between 2.4-98.2 g dry wt. m^-2, with a maximum in June and a minimal in November. In the field, U. prolifera biomass could be positively related to seawater temperature. However, further research on the association between biomass and other environmental factors such as nutrients and light intensity is required.

• KEPCO Journal on Electric Power and Energy
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• v.7 no.2
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• pp.329-333
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• 2021

V2G (Vehicle to Grid) technology for an EV (Electric Vehicle) has been assumed as so promising in a near future for its useful energy resource concept but still yet to be developed around the world for specific service purposes through various R&BD projects. Basically, V2G returns power stored in vehicle at a cheaper or unused time to the grid at more expensive or highly peaked time, and is accordingly supposed to provide such roles like peak shaving or load levelling according to customer load curve, frequency regulation or ancillary reserves, and balancing power fluctuation to grid from the weather-sensitive renewable sources like wind or solar generations. However, it has recently been debated over its prominent usage as diffusing EVs and the required charging/discharging infrastructure, partially for its addition of EV ownership costs with more frequent charging/discharging events and user inconvenience with a relative long-time participation in the previously engaged V2G program. This study suggests that a Korean DR (Demand Response) service integrated V2G system especially based upon a dynamic charge/pause/discharge scheme newly proposed to ISO/IEC 15118 rev. 2 can deal with these concerns with more profitable business model, while fully making up for the additional component (ex. battery) and service costs. It also indicates that the optimum economic, environmental, and grid impacts can be simulated for this V2G-DR service particularly designed for EV aggregators (V2G service providers) by proposing a specific V2G engagement program for the mediated DR service providers and the distributed EV owners.

• Journal of the Korean Geotechnical Society
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• v.23 no.2
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• pp.85-92
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• 2007

As the use of drilled shafts for foundation of a large size structure increases, the evaluation of the reliable bearing capacity of the pile has become important. The purpose of this study is to verify the reliability of bearing capacity equations for drilled shafts socketed in weathered rock by comparing the bearing capacity values from static load tests with values from bearing capacity equations. In this study, twelve data from static load test were selected from four field sites, and the data of load test and the properties of weathered rock were analyzed. Three methods widely used in practice were selected for analysis, namely the AASHTO method (1996), Carter & Kulhawy method (1988), and FHWA method (1999). The comparison of the bearing capacity values from the bearing capacity equations to those obtained from load tests showed that the Carter & Kulhawy method (1988) was the most reliable in giving conservative design values and smaller COV (Coefficient Of Variation).

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.249-249
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• 2021

도시지역의 우수유출해석 모형인 SWMM 모형의 매개변수는 유역유출관련 매개변수와 우수관로 매개변수로 구분이 된다. 이중 우수관로내 수리거동에 영향을 대표적인 매개변수는 조도계수가 있다. 우수관로 조도계수는 우수관로의 규격 및 재료에 따라 적용범위가 제시되어 있지만 현상태 관로내 퇴적 및 협잡물 등에 의한 조도변화가 발생하게 된다. 따라서 본 연구에서는 우수관로 조도계수의 변화에 따른 유량의 민감도를 검토하고 모니터링 유량과 비교를 통한 연구 대상지역의 최적 조도계수를 선정하였다. 연구 대상지역은 울산광역시 삼호동 일대이며 대상지역 내 발생한 우수유출은 최종적으로 태화강으로 방류되는 구조를 갖고 있는 배수분구이다. 조도계수 민감도 분석에 적용한 조도계수의 범위는 일반적인 원형 우수관로의 조도계수 0.013을 기준으로 하고 0.002씩 증감을 시켜 총 6개 CASE에 대한 민감도 분석을 수행하였다. 모의 유량의 비교군이 되는 관측 유량의 경우는 초음파 유량계로 관측한 총 3개 지점의 유량자료를 이용하여 민감도 분석에 활용하였다. 조도계수 민감도 분석결과 조도계수 증가에 따라 첨두유량은 감소하게 된다. 각 지점별 첨두유량 변화 폭은 지점 4, 5, 6에 각각 7.0% (-3.4~3.6%), 14.3% (-7.5~6.8%), 15.6% (-7.7~7.9%) 증감 폭을 갖는 것으로 분석되었으며, 유역의 하류부로 갈수록 변동 폭이 커지는 것으로 분석되었다. 시계열 수문곡선 비교결과 지점 4에서는 조도계수 0.011, 지점 5는 0.013, 지점 7은 0.015를 적용하는 것이 실측치와의 상관계수가 가장 높게 나타나는 것으로 분석되었다. 이상의 분석 결과를 토대로 유역의 관 흐름 상태의 변화는 관로의 퇴적, 부유물, 폐유부착 등의 유지관리 상태에 따라 달라지며 특히 유역의 하류부로 갈수록 퇴적, 부유물 등의 축척이 누적되어 조도계수를 상류부 보다 기준 값보다 크게 적용해야 관측치 유량과 유사하게 모의되는 것을 확인하였다. 따라서 도시유출해석 모형에서의 조도계수 적용은 우수관로의 유지관리 상태 등을 고려하여 우수관로별 적용 값 다르게 입력하는 것이 타당한 것으로 판단된다.

• The Journal of the Acoustical Society of Korea
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• v.43 no.3
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• pp.285-292
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• 2024

When calculating sonar detection probability, underwater acoustic uncertainty is assumed to be normal distributed with a standard deviation of 8 dB to 9 dB. However, due to the variability in experimental areas and ocean environmental conditions, predicting detection performance requires accounting for underwater acoustic uncertainty based on ocean experimental data. In this study, underwater acoustic uncertainty was determined using measured mid-frequency (2.3 kHz, 3 kHz) noise level and transmission loss data collected in the shallow water of the East Sea. After calculating the predictable probability of detection reflecting underwater acoustic uncertainty based on ocean experimental data, we compared it with the conventional detection probability results, as well as the predictable probability of detection results considering the uncertainty of the Rayleigh distribution and a negatively skewed distribution. As a result, we confirmed that differences in the detection area occur depending on each underwater acoustic uncertainty.

• The Journal of the Acoustical Society of Korea
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• v.43 no.4
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• pp.437-444
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• 2024

Bistatic sonar performance varies significantly depending on the ocean environment, the location (latitude, longitude) and water depth of the source and receiver. Therefore, research on optimal deployment of bistatic sonar considering ocean environment is necessary. In this study, we suggest an algorithm to optimize the location and water depth of source and receiver when operating monostatic and bistatic sonar on two spatially separated surface ships in the Ulleung Basin in the East Sea. A particle swarm optimization algorithm was used to search the location and water depth of the source and receiver to maximize the detectable area within the search area. As a result of performing bistatic sonar deployment using the algorithm proposed in this study, the detectable area increased as the number of model iterations increased. Additionally, it was confirmed that the source and receiver on the two surface ships converged to the optimal location and water depth.