• Journal of the Korea Society for Simulation
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• v.16 no.3
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• pp.1-9
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• 2007

Travel time between two points depends upon whether it is a rush hour or not in metropolitan area. It is true that there is big differences on the time required to get through the area whether going in busy morning or near noon. Another issue is that there exist many delivery points which closely located each other; so no need to consider traveling hours among these points. We designed an efficient procedure to reduce the complexity by considering closely located delivery points as one big delivery point. A computer simulation model is constructed for comparison purposes of the developed heuristic with the optimum solution.

• Journal of Global Scholars of Marketing Science
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• v.4
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• pp.213-239
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• 1999

소비자의 욕구와 개성화, 그리고 시장경쟁력에서 생산체제가 변화되면서 기업들의 물류환경여건도 변화를 가져와 물류가 기업들에게 당면한 주요 과제가 되었다. 사회 간접자본의 부족으로 인한 도로, 항만 등의 정체현상이 심화되고 3D업종에 속하는 물류부문은 더욱 인력난을 겪게 되면서 물류비상승이라는 부담을 안게 되었다. 그리고, 컴퓨터, 정보통신기술 등과 같은 첨단의 기술혁신이 이루어 집에 따라 컴퓨터 및 각종 기기들의 연결이 가능해지면서 물류정보시스템 구축이 활발하게 이루어져 가고 있다. 그러나, 이러한 현실에도 불구하고 기업들은 이에 대한 효율적인 대처 방안을 마련하지 못하고 물류에 대한 인식조차 못하고 있거나 잘못 이해하고 있는 실정이다. 본 논문은 이러한 문제점을 인식하여 물류정보시스템의 활용수준과 물류활동 연계 그리고 물류전략에 대한 이론을 정립하고 이를 근거하여 나라 기업률이 물류를 어떻게 인식하고 있는가를 물류정보시스템의 활용수준, 물류활동연계, 물류전략 등의 변수를 도입, 측정하여 봄으로써 우리나라 기업의 물류에 대한 문제점들을 규명하고 앞으로 물류의 능률적인 실시를 위한 올바른 방향을 제시하는데 그 목적을 두고 있다. 실종분석 결과 물류성과에 대한 물류정보시스템 활용수준과 물류연계수준은 물류성과에 영향을 미치는 것으로 나타났다. 그리고, 물류 기능별 정보시스템 활용수준과 물류차별화 전략이 물류성과에 상호작용 효과를 보이는 지를 알아본 결과 상호작용효과가 있는 것으로 나타났다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.843-848
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• 2017

Metal exposed to high temperature/high pressure/oxidizer-rich environment may cause rapid oxidation(ignition and combustion). In this study, a DC power supply test system that controls the temperature of specimen by supplying power to the specimen was constructed and after simulating the high temperature/stagnation/oxidizer-rich environment, the metal oxidation and ignition of STS series metal materials were evaluated. As a result, we was confirmed that the deformation (discoloration) of the selected material, the change in the surface roughness and the peeling of the metal surface were observed, and that the weight and the specimen thickness were changed. The most oxidized specimen was STS 304 and the less oxidized specimen was XM-19.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.8
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• pp.1434-1440
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• 2008

Performance of TCP/IP is studied on the wireless network using flow control and congestion control mechanism based on transmission rate. We discuss the elimination or the reduction of various phenomena of burst by flow controlling on transmission rate and verify that there are TCP ACK compression promblems on the queue by burst reaction while executing transmission rate controlled channels. Analyzing periodic burst reaction on the queue of source IP, the maximum value of queue is expected, which represents the applible expectation of throughput reduce and shows the improvement of performance by the reduce of throughput due to hi-directional traffic.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.4 no.1 s.6
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• pp.43-56
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• 2005

This research has examined a time series analysis(TSA) of an every hour traffic information such as occupancy, a traffic flow, and a speed, a statistical model of a surveyed data on the traffic fundamental diagram and an expand aspect of a traffic jam by many Parts of the traffic flow. Based on the detected data from traffic accidents on the Cheonan-Nonsan high way and events when the road volume decreases dramatically like traffic accidents it can be estimated from the change of occupancy right after accidents. When it comes to a traffic jam like events the changing gap of the occupancy and the mean speed is gentle, in addition to a quickness and an accuracy of a detection by the time series analyse of simple traffic index is weak. When it is a stable flow a relationship between the occupancy and a flow is a linear, which explain a very high reliability. In contrast, a platoon form presented by a wide deviation about an ideal speed of drivers is difficult to express by a statical model in a relationship between the speed and occupancy, In this case the speed drops shifty at 6$\~$8$\%$ occupancy. In case of an unstable flow, it is difficult to adopt a statistical model because the formation-clearance Process of a traffic jam is analyzed in each parts. Taken the formation-clearance process of a traffic jam by 2 parts division into consideration the flow having an accident is transferred to a stopped flow and the occupancy increases dramatically. When the flow recovers from a sloped flow to a free flow the occupancy which has increased dramatically decrease gradually and then traffic flow increases according as the result analyzed traffic flow by the multi regime as time series. When it is on the traffic jam the traffic flow transfers from an impeded free flow to a congested flow and then a jammed flow which is complicated more than on the accidents and the gap of traffic volume in each traffic conditions about a same occupancy is generated huge. This research presents a need of a multi-regime division when analyzing a traffic flow and for the future it needs a fixed quantity division and model about each traffic regimes.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.50-50
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• 2022

한국농어촌공사 산하의 농업용저수지 중 3786개소에 대한 수질조사를 '19년도에 실시한 결과, TOC 기준 4등급 초과 저수지 비율은 약 20%로써, 도심 근교 저수지에서 녹조현상 빈발로 인해 수질, 악취, 미관 등의 환경문제 개선 민원이 다수 발생하고 있다. 현재 녹조 발생 사후관리를 위해 주로 사용되고 있는 대형 조류제거선은 저수심 수변부에서의 적용성에 한계가 있고, Al 기반의 응집제를 사용하여 조류를 수거해서 폐기하고 있는 실정이다. (주)이엔이티는 농어촌연구원, (주)코레드, (주)삼호인넷과 함께 호소나 정체하천의 수변지역에 적용될 수 있는 저에너지형 유해조류 포집시스템 개발과, 수거된 조류부산물을 무독화하여 농업재료로 재활용하는 방안을 연구하고 있다. 저수지나 정체수역의 녹조는 바람, 수면유동 등에 의해 수변에 집적되는 특성이 있어, 인공지능 기술로 녹조현상을 감시하여 조류 밀집구간에 접근할 수 있는 자율이동식 수상이동장치를 개발 중이다. 수상이동장치는 조류포집장치를 탑재하기 위한 부력체, 원격 운전이 가능한 무인항법장치, 수변식생대 및 저수심지역 이동을 고려한 수차방식 추진체, 전체 장치의 전원 공급을 위한 고성능 배터리 등으로 구성하여 상세 도면 설계를 진행하고 있다. 조류포집장치에는 표층에 주로 분포하는 남조류를 선택 흡입하는 포집 부표를 적용하였고, Al계 응집제 사용을 배제한 분리막 실험을 통해 침지형 막분리조 및 가압형 농축조를 설계하였다. 유해조류 포집 및 농축은 수상에서 이동체에 탑재하여 이뤄지고, 육상에서는 자원 회수가 가능하도록 회분식 응집공정으로 구분하였다. 조류 밀집지역에서 수거된 조류의 무독화 및 농업재료 자원화 타당성 평가를 위해 특용 버섯균주를 활용한 시료별 분석항목을 선정하고 실험 매트릭스에 따라 실증실험을 수행하였다. 수거조류를 전처리하여 성분 및 발열량을 분석하고 버섯재배 전후의 마이크로시스틴 독소(LR, RR, LR)를 포함한 성분 분석을 수행하여, 고체연료, 비료 및 사료로 활용방안을 검토하였다. 무인자율이동 조류포집장치는 실증화 규모로 제작하여 기선정된 테스트베드에서 현장적용성 평가를 수행할 예정이다. 본 연구를 통해 개발된 유해조류 포집 시스템은 기존의 녹조제거 방안을 보완하여 정체수역의 생태계 복원 및 친수공간의 환경개선 등에 적용되며, 무독화가 입증된 유해조류의 농업재료 자원화 기술은 고부가 상품 개발 및 환경폐기물 감축에 활용될 것이다.

• Journal of Korea Water Resources Association
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• v.57 no.4
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• pp.263-276
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• 2024

Since the first introduction of one-dimensional transient storage modeling in the field of solute transport analysis in rivers, its application has notably expanded for various purposes, including for hydrology and geobiology over the past few decades. Despite strides in refining transient storage models, there remain unresolved challenges in simplifying complex river transport dynamics into concise formulas and a limited set of parameters. This review paper is dedicated to cataloging and assessing existing transient storage models, outlining the difficulties associated with model structures, parameters, and data, and suggesting directions for future research. We seek to enhance understanding of transient storage by highlighting the importance of continuously evaluating residence time distribution modeling, integrating hydrodynamic models, and using data with minimal assumptions. This paper would contribute to advance our comprehension of the transient storage process, offering insights into sophisticated modeling techniques, pinpointing uncertainty in parameters, and suggesting the necessary avenues for further study.

• Journal of the Korean Society of Propulsion Engineers
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• v.1 no.1
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• pp.64-72
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• 1997

An analytical study has been performed to investigate the unsteady ignition characteristics of pulse combustion. In many combustion applications, strain rate of the flow can significantly affect the combustion features; ignition, extinction, and reignition. In the pulse combustion, two jets (hot combustion gases and fresh mixtures) coming from the opposite side of the combustor will collide in the combustor forming a stagnation region where the chemical reaction is suppressed by the strain rate until this becomes below the critical value. In this research, the method of large activation energy asymptotic is adopted with one step irreversible kinetics to examine the ignition response to the periodic variation of the strain rate of flow. The results show the variation of the maximum value of strain rate can determine whether the ignition or extinction occur.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.533-537
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• 2017

우리나라는 2012년에 4대강 사업을 통하여 수자원확보를 통한 가뭄대응전략으로 16개의 대형보가 건설되었고 영산강에는 승촌보와 죽산보 2개의 보가 건설되었다. 보의 건설로 흐름은 급격히 감소하여 정체구역의 수역이 확장되면서 여름에서 초가을까지 녹조현상은 매년 지속적으로 발생하고 있으며, 최근 국민들은 안전한 농산물의 안정적인 생산에 요구가 점증함에 따라 농업용수질 오염문제가 범국가적 문제로 대두되고 있고, 그 중요도 및 심각성이 점차 커져가고 있다(한강유역환경청, 2007). 많은 량의 물을 농업용수로 사용하고 있는 영산강의 녹조현상 및 수질개선이 절실하다. 따라서 본 연구에서는 영산강의 승촌보와 죽산보의 건설과 수질오염총량관리제의 시행에 따른 부영양화특성의 변화를 파악하기 위하여 환경부, 국립환경과학원(2006)에서 개발한 한국형 부영양화지수(TSIko) 평가법을 이용하여 영산강유역의 12개 주요지점에 대하여 수집한 자료를 봄(3월~5월), 여름(6월~8월), 가을(9월~11월), 겨울(12월~2월)로 분리하고, 다시 4대강 사업의 영향을 검토하기 위하여 2013년을 전후하여 분리하였으며, 계절별 수질인자 COD, T-P, Chl-a 값을 이용하여 계절별 $TSI_{Ko}$를 산정하여 영양상태를 4개의 등급으로 구분하여 부영양화특성을 파악하였다.

• Journal of the Korean Geographical Society
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• v.30 no.3
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• pp.230-241
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• 1995

The Characteristics of nocturnal temperature fields were analyzed to understand the factors of freezing-and-cold damages on orange orchards in Cheju Island. Temperatures were measured from January 7th through 27, 1995 at 25 sites in an area of 1x1.25$ extrm{km}^2$, Wasan-ri, Chochon-up, Pukcheju-kun located on the northeastern slope of Mt.Hanla. Several other weather elements such as wind and cloud were observed as supplementary data. Surface weather maps were also analyzed to clarify the influence of prevailing pressure patterns on the temperature fields. The vertical temperature profiles were obtained at the height from the ground up to 360 cm in 30 cm intervals at site 3, a frost hollow, and site 10 on the upper slope. The results show that freezing damages occured in the hollows, terrain depressions, rather than at the upper slope due to nocturnal radiation cooling as well as accumulation of cold airflow from Mt.Hanla. Windbreaks of densely planted Japanese ceders with stone-walls also roled as obstacles to the cold airflow in nights with Clear skies and light winds. The maximum intensity of temperature inversion in hollows, quasi-cold air lake, was 3.1$^{\circ}C$. Cold air from Mt.Hanla was trapped in the depressions up to a height of 90cm forming frost pocket. Man-made facilities such as shelterbelt or stone-wall which are built to prevent the penetration of cold north-westeries in winter aggravated the cold damage. The differance of daily minimum temperatures between before and behind shelterbelts was 2.$0^{\circ}C$. The man-made convection by smudgin which raised the temperatures up to 3.8$^{\circ}C$ can reduce the cold damage in the hellows.