• Journal of Ocean Engineering and Technology
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• v.10 no.3
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• pp.138-152
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• 1996

Many studies of heat transfer on the swirling flow or unswirled flow in a abrupt pipe expansion are widely carried out. The mechanism is not fully found evidently due to the instabilities of flow in a sudden change of the shape and appearance of turbulent shear layers in a recirculation region and secondary vortex near the corner. The purpose of this study is to obtain data through an experimental study of the swirling flow and heat transfer downstream of an abrupt expansion in a circular pipe with uniform heat flux. Experiments were carried out for the turbulent flow nd heat transfer downstream of an abrupt circular pipe expansion. The uniform heat flux condition was imposed to the downstream of the abrupt expansion by using an electrically heated pipe. Experimental data are presented for local heat transfer rates and local axial velocities in the tube downstream of an abrupt 3:1 & 2:1 expansion. Air was used as the working fluid in the upstream tube, the Reynolds number was varied from 60, 00 to 120, 000 and the swirl number range (based on the swirl chamber geometry, i.e. L/d ratio) in which the experiments were conducted were L/d=0, 8 and 16. Axial velocity increased rapidly at r/R=0.35 in the abrupt concentric expansion turbulent flow through the test tube in unswirled flow. It showed that with increasing axial distance the highest axial velocities move toward the tube wall in the case of the swirling flow abrupt expansion. A uniform wall heat flux boundary condition was employed, which resulted in wall-to-bulk temperatures ranging from 24.deg. C to 71.deg. C. In swirling flow, the wall temperature showed a greater increase at L/d=16 than any other L/d. The bulk temperature showed a minimum value at the pipe inlet, it also exhibited a linear increase with axial distance along the pipe. As swirl intensity increased, the location of peak Nu numbers was observed to shift from 4 to 1 step heights downstream of the expansion. This upstream movement of the maximum Nusselt number was accompanied by an increase in its magnitude from 2.2 to 8.8 times larger than fully developed tube flow values.

• Journal of Korean Society of Environmental Engineers
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• v.38 no.5
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• pp.255-268
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• 2016

Climate change has increased the need to secure a new water resource in addition to the traditional water resources such as surface water and ground water. The seawater desalination market is growing sharply in accordance with this situation in Korea, "seawater engineering & architecture of high efficiency reverse osmosis (SEAHERO)" program was launched in 2007 to keep pace with world market trend. SEAHERO program was completed in 2014, contributed to turn the domestic technology in evaporative desalination technology to RO desalination technology. Currently, it is investigated that the average specific energy consumption of the whole RO plant is around $3.5kWh/m^3$. The Busan Gi-jang plant has shown $3.7{\sim}4.0kWh/m^3$, including operational electricity for plant and maintenance building. Although not world top level, domestic RO technology is considered to be able to compete in desalination market. Separately, many researchers in the world are developing new technologies for energy savings. Various processes, forward osmosis (FO), membrane distillation (MD) process are expected to compete with RO in the future market. In Korea, FO-RO hybrid process, MD and pressure retarded osmosis (PRO) process are under development through the research program in Ministry of Land, Infrastructure and Transport (MOLIT). The desalination technology level is expected to decrease to $2.5kWh/m^3$.

• Korean Journal of Agricultural Science
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• v.36 no.2
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• pp.135-145
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• 2009

This research was conducted to investigate the effect of various phosphorus concentrations in fertilizer solution on growth of and nutrient uptake by 'Chugyang' egg plant (Solanum melongena L.). Tissue and soil analyses were also conducted to set the threshold levels of phosphorus in plants when disorders develop for phosphorus deficiency or excess. Brown and purple areas developed on the margin of mature leaves and it enlarged rapidly in P deficient plants. The fruits in P deficient plants were small and dull purple in color. When P were excess in fertigation solution, the margins of lower leaves became scorched and it enlarged to inner part of the leaves. The fruits of P excess plants became small and had the curl shape. The tissue $PO_4$-P contents in the most recently fully expanded leaves and dry weight of full above ground plant tissue at 35 days after transplanting showed quadratic response ($y=0.7887+0.2394x-0.0197x^2$) and cubic response ($y=10.43+14.47x-4.7642x^2+0.3977x^3$) to elevated $PO_4$-P concentrations, respectively. When 10% reduction in dry weight set to threshold levels, optimum tissue $PO_4$-P contents are between 0.98 to 1.35%. The yield determined at 150 days after transplanting also showed cubic response to elevated phosphorus concentrations in fertigation solution ($y=1194.6+1502.2x-454.5x^2+35.64x^3$). When the 10% reduction in yield is set to threshold levels, the tissue $PO_4$-P contents for maximum yield should be around 1.53% to 2.25% in most recently fully expanded leaves at 150 days after transplanting.

• The Korean Journal of Air & Space Law and Policy
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• v.31 no.2
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• pp.3-35
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• 2016

The United States Constitution gives power to the federal district courts to hear admiralty cases. 28 U.S.C. §.133, which states that "The district courts shall have original jurisdiction, exclusive of the Courts of the States, of any civil case of admiralty or maritime jurisdiction." However, the determination of whether a case is about admiralty or maritime so that triggers admiralty jurisdiction was not a simple question. Through numerous legal precedents, the courts have drawn a line to clarify the boundary of admiralty cases. This unique jurisdiction is not determined by the mere involvement of a vessel in the case or even by the occurrence of an event on a waterway. As a general rule, a case is within admiralty jurisdiction if it arises from an accident on the navigable waters of the United States (locus test) and involves some aspect of maritime commerce (nexus test). With regarding to the maritime nexus requirement, the US Supreme Court case, Executive Jet Aviation, Inc. v. City of Cleveland, held that federal courts lacked admiralty jurisdiction over an aviation tort claim where a plane during a flight wholly within the US crashed in Lake Erie. Although maritime locus was present, the Court excluded admiralty jurisdiction because the incident was "only fortuitously and incidentally connected to navigable waters" and bore "no relationship to traditional maritime activity." However, this historical case left a milestone question: whether an aircraft disaster occurred on navigable water triggers the admiralty jurisdiction, only for the reason that it was for international transportation? This article is to explore the meaning of admiralty jurisdiction over aviation accidents at US courts. Given that the aircraft engaged in transportation of passenger and goods as the vessels did in the past, the aviation has been linked closely with the traditional maritime activities. From this view, this article reviews a decision delivered by the Seventh Circuit regarding the aviation accident occurred on July 6, 2013 at San Francisco International Airport.

• Bulletin of the Society of Naval Architects of Korea
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• v.61 no.1
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• pp.16-29
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• 2024

2014년 4월 18일 오전 8시 48분경 전라남도 병풍도 인근 해역에서 세월호는 전복된 후 침몰하였다. 사고 당시 이 배에는 승객 443명과 선원 및 승무원 33명 모두 476명이 타고 있었고, 이 중 미수습자 5명을 포함하여304명이 생명을 잃었다. 그 동안 공식적인 사고원인 규명활동이 꾸준히 진행되어 이 사고의 원인을 규명하기 위한 조사가 네 차례 있었다. 하지만 아직까지 사고 원인이 무엇인지 명쾌하게 밝혀지지 않고 있다. 이 글에서는 먼저 그동안 있었던 네 차례의 공식적인 세월호 사고원인 규명활동을 정리하였다. 가장 먼저 사고원인 규명활동을 전개한 해양안전심판원 특별조사부는 2014년 사고 직후부터 그해 12월까지 활동하였다. 특별조사부 최종보고서에는 화물의 과적과 평형수 적재 부족으로 인한 선박복원성 기준 미달, 타각의 대각도 조타와 장시간 유지로 인한 부적절한 조타, 화물의 부실한 고박으로 인한 화물의 이동, 수밀문의 관리 부실로 인한 조기 침수와 비상대피장소(muster station)로의 승객대피 조치 미이행을 사고의 원인으로 들고 있다. 2015년 3월부터 2016년 6월까지 활동한 4·16세월호참사 특별조사위원회(특조위)는 '4·16 세월호 참사 특별 조사위원회 청산 백서'만을 간행하고 최종보고서를 제출하지 못한 채 활동을 종료하였다. 세월호 선체조사위원회(선조위)는 2017년 4월부터 2018년 8월까지 활동하였다. 선조위는 세월호 사고원인 규명을 위한 다른 기구에 비해 위원의 구성도 균형이 있었고, 직권사건 위주의 조사방법도 적절하였다. 또한 조타기와 조타 과실 여부, 급선회 항적 및 횡경사와 핀안정기의 물리적 손상에 관한 용역을 국내 여러 기관에 발주하였다. 뿐만 아니라 다양한 해양사고 원인규명 용역에 참여한 실적이 있는 영국의 기술용역회사인 Brookes Bell에 급선회와 빠른 침몰의 원인 조사를 요청하였다. 아울러 세계에서 가장 활발히 수조실험을 수행하고 있는 상업 연구소인 네덜란드의 MARIN에 수조시험과 시뮬레이션도 의뢰하였다. 하지만 아쉽게도 선조위는 서로 다른 사고 원인을 주장하는 두 권의 종합보고서를 간행하였다. 종합보고서로 '내인설' 종합보고서[6]는 타기 솔레노이드 밸브의 고착으로 시작된 급선회를 사고의 직접 원인으로 지목하고 있다. 하지만 '열린안' 종합보고서[7]에서는 수중체와의 충돌을 직접적인 사고 원인으로 밝히고 있다. 마지막으로 가습기살균제 사건과 4·16세월호 참사 특별조사위원회(사참위)가 2019년 3월부터 2022년 9월까지 활동하였다. 사참위는 위원으로 조선해양공학과 항해학 전문가가 포함되어 있지 않아 세월호의 사고원인 규명활동을 효과적으로 수행하기에는 적절하지 못하였다. 사참위는 주로 조타장치 고장에 따른 세월호 전타 선회현상 검증, 세월호 변형 손상부의 확인 및 원인 조사와 세월호 횡경사 원인과 침수과정 분석을 직권 과제로 추진하였다. 또한 네덜란드 MARIN에 자유항주시험을 추가로 의뢰하였으며, 핀란드의 NAPA group에도 복원성 계산과 침수해석을 의뢰하였다. 사참위는 선조위의 두 가지 사고원인에 대해 '내인설'의 솔레노이드 밸브 고착은 사고원인일 가능성이 매우 낮고, '열린안'의 수중체와의 충돌 시나리오는 근거가 부족함을 확인하였다. 이상에서 정리한 바와 같이 규명활동이 진행됨에 따라 사고원인이 수렴되어야 함에도 불구하고 아직까지 원인을 시원하게 밝히지 못하고 있다. 이 글에서는 사고원인 규명활동을 수행한 네 개 기구의 구성과 활동 내용을 비교하고, 사고조사 위원회의 바람직한 구성과 위원회의 운영 방법을 제시하고 있다. 또한 Brookes Bell 보고서에 수록된 출항 당시의 흘수에 근거한 배수량과 선미 램프의 폐쇄 전후의 횡경사각으로부터 도출한 GoM도 소개하고 있다. 아울러 출항 당시의 GoM값으로 추정한 사고 당시의 GoM값도 소개하고 있고, 수중체와의 충돌 시나리오를 후보 사고 시나리오에서 제외시켜야 할 이유도 열거하고 있다. 끝으로 해양사고 원인규명 활동이 보다 과학적으로 그리고 보다 합리적으로 이루어질 수 있기 위해 그리고 우리 사회의 안전문화 제고를 위한 몇 가지의 방안을 제시하고 있다. 또한 세월호 사고로 치른, 아직도 치르고 있는 희생을 딛고 해양안전문화가 한 걸음 더 나아가기 위해서는 세월호 사고의 원인을 반드시 규명해야 한다는 말씀으로 글을 마무리하고 있다.

• The Korean Journal of Air & Space Law and Policy
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• v.31 no.2
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• pp.145-176
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• 2016

Aviation safety can be secured through regulations and policies of various areas and thorough execution of them on the field. Recently, for aviation safety management Korea is making efforts to prevent aviation accidents by taking various measures: such as selecting and promoting major strategic goals for each sector; establishing National Aviation Safety Program, including the Second Basic Plan for Aviation Policy; and improving aviation related legislations. Obstacle limitation surface is to be established and publicly notified to ensure safe take-off and landing as well as aviation safety during the circling of aircraft around airports. This study intends to review current aviation obstacle management system which was designed to make sure that buildings and structures do not exceed the height of obstacle limitation surface and identify its operating problems based on my field experience. Also, in this study, I would like to propose ways to improve the system in legal and regulatory aspects. Nowadays, due to the request of residents in the vicinity of airports, discussions and studies on aviational review are being actively carried out. Also, related ordinance and specific procedures will be established soon. However, in addition to this, I would like to propose the ways to improve shortcomings of current system caused by the lack of regulations and legislations for obstacle management. In order to execute obstacle limitation surface regulation, there has to be limits on constructing new buildings, causing real restriction for the residents living in the vicinity of airports on exercising their property rights. In this sense, it is regarded as a sensitive issue since a number of related civil complaints are filed and swift but accurate decision making is required. According to Aviation Act, currently airport operators are handling this task under the cooperation with local governments. Thus, administrative activities of local governments that have the authority to give permits for installation of buildings and structures are critically important. The law requires to carry out precise surveying of vast area and to report the outcome to the government every five years. However, there can be many problems, such as changes in the number of obstacles due to the error in the survey, or failure to apply for consultation with local governments on the exercise of construction permission. However, there is neither standards for allowable errors, preventive measures, nor penalty for the violation of appropriate procedures. As such, only follow-up measures can be taken. Nevertheless, once construction of a building is completed violating the obstacle limitation surface, practically it is difficult to take any measures, including the elimination of the building, because the owner of the building would have been following legal process for the construction by getting permit from the government. In order to address this problem, I believe penalty provision for the violation of Aviation Act needs to be added. Also, it is required to apply the same standards of allowable error stipulated in Building Act to precise surveying in the aviation field. Hence, I would like to propose the ways to improve current system in an effective manner.