• Journal of Aerospace System Engineering
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• v.18 no.1
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• pp.72-78
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• 2024

It is essential to coincide with moving target planet at future arrival changing point during space flight time in an interplanetary orbit design. Transition orbit elements can be obtained from traditional Lambert solutions by adjusting initial and final positions include flight time. Two-point boundary values of orbits can be selected in the design process. From this point of view, interplanetary orbits are infinite if they can be acquired from departure velocity without limit. However, appropriate and optimized procedures are needed to obtain an optimum interplanetary orbit to meet given conditions. The departure velocity is highly dependent on space launch vehicle's ability up to now. In this paper, algorithms of professor Howard Curtis at Embry-Riddle Aeronautical University were applied to obtain Lambert solution and orbit elements.

• Journal of the Korean Association of Geographic Information Studies
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• v.24 no.3
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• pp.41-57
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• 2021

This study evaluated the application of water quality management measures using the SWAT model and the effectiveness of the measures using the load duration curve targeting the Seohwacheon watershed located upstream of Daecheongho. As water quality management measures, artificial wetlands, reduction of neglected livestock, reduction of runoff from greenhouses, restoration of ecological rivers, application of LID technology, and management of point sources were applied. The applied technology evaluated the efficiency of water quality improvement measures by using the target water quality excess rate and the degree of load reduction for each sulfur through the load duration curve. The load duration curve was created by creating a long-term flow duration curve using SWAT and multiplying it by the target water quality. For the target water quality, the value corresponding to the 60th percentile was set as the target water quality using the 10-year data from the Okcheoncheon water quality observation point located in the downstream of Seohwacheon. Through this study, it was possible to confirm the applicability of various water quality measures through the SWAT model, and to examine the applicability of each period according to the sulfur through the load retention curve.

• Journal of Wetlands Research
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• v.25 no.4
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• pp.326-334
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• 2023

The purpose of this study is to use long-term water quality monitoring data from tributaries of the Nakdong River system to identify problematic substances in tributaries by examining the rate of exceedance and increase in water quality targets. In the Nakdong River system, monitoring is conducted once a month for 38 tributaries that require intensive management, and this data was used to analyze trends in exceeding and increasing target water quality at each point. The analysis items are eight items that can be evaluated based on river water quality standards: DO, BOD, COD, TOC, SS, total phosphorus, fecal coliform, and total coliform. As a result of the analysis, the target water quality exceedance rate was more than 50%, and the items with an increasing trend were TOC, fecal coliform and total E. coli counts, and the items with an exceedance rate of less than 50% but an increasing trend were SS. TOC is believed to be caused by an increase in non-degradable substances, and the continued increase in Total Coliform will require management of Total ColiformTotal Coliform in effluent water from sewage treatment facilities in the future.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.6
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• pp.55-62
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• 2010

Monitoring systems are able to report certain events at region of interest(ROI) and to take an appropriate action. From industrial product line full of robots to fire detection, intrusion detection, smart grid application, environmental pollution alarm system, monitoring system has widely used in diverse industry sector. Recently, due to advance of wireless communication technology and availability of low cost sensors, intelligent and/or smart monitoring systems such as sensor networks has been developed. Several deployment methods are introduced to meet various monitoring needs and deployment performance criteria are also summarized to be used to identify weak point and be useful at designing monitoring systems. Both efficiency during deployment and usefulness after the deployment should be assessed. Efficiency factors during deployment are elapsed time, energy required, deployment cost, safety, sensor node failure rate, scalability. Usefulness factors after deployment are ROI coverage, connectivity, uniformity, target density similarity, energy consumption rate per unit time and so on.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.1494-1498
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• 2009

세계기상기구(WMO)에 의하여 홍수예경보시스템의 평가를 위하여 개발된 MOFFS Ver.3의 개선을 위하여 특정유역의 홍수방어체계의 취약성을 평가하고 홍수방어시스템의 완성도를 높이기위한 DSS-FOP를 개발하였다. DSS-FOP는 지점별, 홍수사상별로 예보시스템 운영결과를 간단한 평가양식에 나타내는 시스템이며, 홍수방어구조물(Flood control infra)과 홍수조절운영(Flood control operation)으로 분류한다. 홍수방어구조물은 수문관측, 홍수방어구조물, 홍수조절지휘소로, 홍수조절 운영은 자료처리 및 전송, 홍수예측모형, 예경보발령의 총 6가지 주요평가항목과 하부의 23가지 세부평가항목으로 구성하였다. 점수부여체계는 최대점수, 목표점수, 성과점수, 부족점수, 취약점수의 산정을 통하여 구조물인프라와 운영측면에서의 시스템취약부분을 평가 진단할 수 있도록 하였다. 개발된 DSS-FOP를 이용하여 국내의 한강유역과 UN/ESCAP 태풍위원회의 회원국인 태국의 Khlong U-Taphao 유역을 대상으로 적용하고 그 결과를 비교 평가하였다. 한강유역의 경우 하천정보센터 신설 및 조직강화로 인적자원측면에서 높은 성과점수를 보였으며, 향후 수문레이더 설치 등으로 관측분야에서의 개선이 기대된다. 태국의 Khlong U-Taphao 유역의 경우 목표수준을 다소 조정할 필요가 있으며, 비상행동계획의 마련이 시급하다. 더불어 홍수방어구조물에 대한 지속적인 투자가 필요한 상황이다. 이러한 DSS-FOP의 평가결과는 국가별, 유역별, 호우사상별로 관리되며, 태풍위원회 회원국의 적용 및 기술지침의 작성을 위해 많은 평가 및 조사가 축적되어야 한다.

• Journal of Navigation and Port Research
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• v.31 no.6
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• pp.515-521
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• 2007

To increase the stevedore efficiency and service level at container terminal, it is essential to reduce working time of container crane which has a bottle neck in the logistic flow of container. The working speed and safety are required to be improved by controlling the movement of the trolley as quick as possible without big overshoot and any residual swing motion of container in the vicinity of target position. This paper presents optimal state feedback control using RCGAs in the case of existing constrained conditions

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.2
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• pp.168-179
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• 2013

The critical point analysis(CA) and impedance matching analysis(IA) are performed and compared for a 4-coil magnetic resonance wireless power transfer system. Because the operating frequency splits at short distance while the efficiency drops drastically at long distance in this system, the optimization technique is needed for either a specific distance or efficiency at the fixed frequency. CA uses the critical point where shows maximum efficiency in the entire range and IA uses the impedance matching technique to achieve maximum efficiency at the specific distance. Comparison result shows that IA is more efficient than CA. Also, it shows one side matching has a tradeoff relationship comparing to both side matching. By using four spiral resonant coils, the analysis was experimentally verified. The measured data agreed well with the calculated data.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.43-43
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• 2011

최근 컴퓨터 기술의 발전으로 수심방향으로 완전한 운동방정식인 Navier-Stokes 방정식을 이용하는 3차원 수치모형에 의한 연구가 기초과학 분야인 수학에서부터 공학은 물론 의학 분야까지 광범위하게 진행되고 있다. 3차원 수치모형을 이용한 연구는 이론적으로 매우 우수하긴 하나 정확도 높은 결과를 얻기 위해서는 매우 조밀한 격자를 필요로 하기 때문에 아직까지 막대한 계산시간이 필요하다는 단점이 있으나 근래의 컴퓨터 기술이 엄청난 속도로 발전하고 있는 점을 감안할 때 적용 가능성은 계속 높아지고 있다. 이러한 흐름에 따라 해안공학 분야에서도 3차원 수치모형을 이용한 다양한 연구가 시도되고 있다. 복잡한 해안구조물로 인한 파랑변형 및 구조물의 안전성 등을 검토할 때 기존의 평면 2차원 수치모형이나 연직 2차원 수치모형으로는 재현이 힘들어 상대적으로 수치모형을 활용한 연구의 효용성이 낮았던 것에 비해 3차원 수치모형을 활용할 경우 복잡한 지형 및 구조물의 형상을 재현할 수 있기 때문에 좀 더 유용하게 사용될 수 있다. 한편, 파랑변형을 다루는 수치모형실험을 수행할 때 외부조파를 사용할 경우 구조물이나 지형에 의해 반사되어 나온 파랑이 조파지점에 도달할 때 실험영역으로 재 반사되는 문제가 발생한다. 이를 해결하기 위해 내부조파기법의 개발에 대한 연구가 필수적이었으며, 2차원 수치모형을 중심으로 그 연구가 매우 활발하게 진행되어 왔으나 Navier-Stokes 방정식 모형의 경우 상대적으로 연구가 미흡하였다. 본 연구에서는 3차원 Navier-Stokes 방정식 모형에서 내부조파기법을 도입하여 목표 파랑을 조파하였다. 수치모형은 Navier-Stokes 방정식을 엇갈림 격자체계에서 계산하는 유한차분모형으로 자유수면 추적에는 2차 정확도의 VOF(volume-of-fluid) 기법을 사용한다. 수치모형실험 결과를 일정한 수심을 전파하는 정현파의 해석해와 비교하였으며, 수치모형실험 결과가 비교적 정확하게 목표 파랑을 조파할 수 있음을 검증하였다.

• Korean Journal of Ecology and Environment
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• v.43 no.2
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• pp.338-344
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• 2010

The automatic water quality monitoring system (AWQMS) have been installed to immediately response to any pollution incident. It also make it possible to conduct the task efficiently regarding water quality control. The purpose of this study is to enhance reliability by securing accuracy of automatic water quality data through quality assessment (QA) for temperature, pH, dissolved oxygen (DO), electric conductivity (EC), total organic carbon (TOC). The result of comparison between manual and automatic data, relative accuracy of general items (temperature, pH, EC, DO) and TOC were mostly satisfied with guideline (i.e. less than 20%). On the other hand, relative accuracy of DO between sampling site and housing site was somewhat against the guideline. The contamination by attaching algae and microorganism in the pipeline is considered as main cause. After backwashing the pipeline, DO concentration was increased up to 53%. Therefore, pipeline management is recognizable as important thing to secure reliability of water quality data.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.4
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• pp.83-90
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• 2018

Considering the increased threats from worldwide terrors and the increased demands on the blast resistant design of commercial buildings, this study is aimed at understanding the basic concept of blast resistant design and evaluating the blast performance with an actual design example. Although there are many differences between earthquake and blast loads, the design concept against both loads is similar in terms of allowing the plastic behavior of a structure and sharing the ductile detailing. Through the blast performance evaluation of a target building provided in this study, it is noted that a well-designed building for the conventional loads can have a certain level of blast resistance. However, this cannot be generalized since the blast load on a structure varies depending on the type of weapon, TNT equivalence, standoff distance, etc. Architectural planning with positioning the sacrificial structure or maintaining a sufficient standoff distance from the expected detonation is the simple and effective way of improving the blast resistance of a building.