• 해양환경안전학회지
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• 제19권4호
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• pp.397-402
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• 2013

본 연구에서는 전장이 26.75 m인 해양플랜트지원선의 선형개발을 위한 수치해석을 수행하였고 수치해석 검증을 위한 1/10의 모형선 시험을 예인수조에서 수행하였다. 또한 운항해역의 해상조건으로 뷰포트 스케일 2, 3 및 4에서 향파, 선수사파 및 횡파에서 선속별 상하동요 및 종동요에 대해서 운동응답특성을 수치 해석하였다. 모형시험과 수치해석의 저항 예측 결과는 상호 일치하였다. 운동응답특성은 선수파에서 상하동요는 조우주파수 1.8~2.0 영역에서 크게 나타났으며, 종동요는 거친 해상에서 선미사파 및 고속영역에서 높은 운동특성을 보였다.

• 해양환경안전학회지
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• 제19권5호
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• pp.497-502
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• 2013

현재 우리나라에서 사용되고 있는 등부표의 종류는 10가지 정도이며, 부표 설계 및 개발의 대부분을 외국 기술에 의존하고 있는 실정이다. 본 연구에서는 해상 계측 등이 가능한 소형 등부표의 개발을 목표로 소형 부표의 설계안을 제시하고 그 안전성을 수치적으로 검토하였다. 구체적으로는 다양한 실제 해상환경과 유사한 조우각과 선속 변화에 따른 내항성과 관련된 응답 진폭비, 부가저항 등의 값을 수치적으로 시뮬레이션하였다. 설계된 부표의 응답해석 결과, 종요응답비가 조우주파수의 증가에 따라 전체적으로 감소하는 특성을 확인하였다. 횡파에 대한 부가저항이 가장 크게 나타나는 것으로 분석되었고, 최종적으로 제시된 부표가 일정 조건하에서 응답 특성이 확보됨을 확인하였다.

• 대한조선학회지
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• 제25권2호
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• pp.11-18
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• 1988

The radiation problem for an oscillating cylinder advancing under the free surface with a constant horizontal velocity is studied using the Green integral equation in the frequency domain. The Green function expressed in terms of the complex exponential, is derived using the damped free surface condition. Special attention is given to the behavior of the numerical solution in the vicinity of the critical Brard number ${\gamma}_c=\omega{\cdot}u/g=0.25$ where $\omega$ is the circular frequency of encounter, u the advancing speed and g the gravitational acceleration. It is shown that the solution is finite in the vicinity of ${\gamma}_c$ although the Green function becomes singular at ${\gamma}_c$. It is also shown that the computed hydrodynamic coefficients agree well with those obtained from the solution of the same problem formulated in the time domain.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제18권7호
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• pp.1907-1928
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• 2024

In recent years, multi-focus image fusion has emerged as a prominent area of research, with transformers gaining recognition in the field of image processing. Current approaches encounter challenges such as boundary artifacts, loss of detailed information, and inaccurate localization of focused regions, leading to suboptimal fusion outcomes necessitating subsequent post-processing interventions. To address these issues, this paper introduces a novel multi-focus image fusion technique leveraging the Swin Transformer architecture. This method integrates a frequency layer utilizing Wavelet Transform, enhancing performance in comparison to conventional Swin Transformer configurations. Additionally, to mitigate the deficiency of local detail information within the attention mechanism, Convolutional Neural Networks (CNN) are incorporated to enhance region recognition accuracy. Comparative evaluations of various fusion methods across three datasets were conducted in the paper. The experimental findings demonstrate that the proposed model outperformed existing techniques, yielding superior quality in the resultant fused images.

• Ocean Systems Engineering
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• 제10권3호
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• pp.317-332
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• 2020

This study examines the behaviors and properties of discharged liquid CO₂ from a long elastic pipe moving with a vessel for the oceanic CO₂ sequestration by considering pipe dynamics and vessel motions. The coupled vessel-pipe dynamic analysis for a typical configuration is done in the frequency and time domain using the ORCAFLEX program. The system's characteristics, such as vessel RAOs and pipe-axial-velocity transfer function, are identified by applying a broadband white noise wave spectrum to the vessel-pipe dynamic system. The frequency shift of the vessel's RAO due to the encounter-frequency effect is also investigated through the system identification method. Additionally, the time histories of the tip-of-pipe velocities, along with the corresponding discharged droplet size and Weber numbers, are generated for two different sea states. The comparison between the stiff non-oscillating pipe with the flexible oscillating pipe shows the effect of the vessel and pipe dynamics to the discharged CO₂ droplet size and Weber number. The pipe's axial-mode resonance is the leading cause of the fluctuation of the discharged CO₂ properties. The significant variation of the discharged CO₂ properties observed in this study shows the importance of considering the vessel-pipe motions when designing oceanic CO₂ sequestration strategy, including suitable sequestration locations, discharge rate, towing speed, and sea states.

• 대한조선학회논문집
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• 제48권4호
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• pp.299-307
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• 2011

The offshore plants such as FPSO are subjected to combination loading of environmental conditions (swell, wave, wind and current). Therefore the fatigue damage is occurred in the operation time because the units encounter the environmental phenomena and the structural configurations are complicated. This paper is a research for frequency domain fatigue analysis of wide-band random loading focused on accuracy of fatigue damage estimation regarding the proposed methods. We selected ideal bi-modal spectrum. And comparison between time-domain fatigue analysis and frequency-domain fatigue analyses are conducted through the fatigue damage ratio. Fatigue damage ratios according to Vanmarcke's bandwidth parameter are founded for wide-band. Considering safety, we recommend that Jiao-Moan and Tovo-Benasciutti methods are optimal way at the fatigue design for wide-band response. But, it is important that these methods based on frequency-domain unstably change the accuracy according to the material parameter of S-N curve. This study will be background and guidance for the new frequency-domain fatigue analysis development in the future.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2010년도 춘계학술대회
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• pp.385-386
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• 2010

선박의 상하동요 및 종동요 간의 내항성능은 승객에게 피로감을 주며, 적재된 화물과 선체에 탑재된 재설비에 구조적 하중을 가져오게 된다. 이러한 점을 개선하기 위해 소형 카타마란 파워요트 설계시 해당 실적선 조사와 선저형상을 결정하여 선형을 설계하였다. 본 연구에서는 국내 연안의 해양환경에 대한 기초자료를 토대로 운동성능 해석조건을 선정하였다. 이를 통해 카타마란형 레저선박의 운동성능을 선속에 따라 고찰하였다. 파도와 선박의 만남각에 따른 내항성능을 추정하여, 파랑의 만남주파수에 대한 응답진폭비와 운동성능이 우수한 영역에 대해서 평가하였다.

• 한국콘텐츠학회논문지
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• 제18권10호
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• pp.478-489
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• 2018

본 연구에서는 사용자의 현재와 기대 스크립트를 기반으로 커피 전문점의 서비스디자인을 위한 규준 스크립트를 설계하였다. 1) 현재와 기대 스크립트에 포함된 활동들을 확인하였다. 2) 현재와 기대 스크립트에서 고빈도의 활동들을 선정하였다. 그런 후 이 둘을 통합하여 장면별로 분류하였다. 3) 통합된 장면과 활동들에 대한 중요도를 평가하였다. 4) 일정한 규칙에 따라 불필요한 활동들을 삭제하거나 선택 항목으로 제외하였다. 그리고 나머지 활동들을 장면별로 분류하고 순서대로 나열하여 하나의 규준 스크립트를 완성하였다. 각 장면에 속한 활동들 하나하나가 서비스 접점이 되었다. 장면은 '들어가기', '자리 정하기', '주문하기', '음료 기다리기', '음료 받기', '음료를 마시며 시간 보내기', '화장실 가기', 그리고 '나가기'로 구성되었다. '들어가기'에는 2개, '자리 정하기'에는 6개, '주문하기'에는 11개, '음료 기다리기'에는 2개, '음료 받기'에는 4개, '음료를 마시며 시간 보내기'에는 6개, '화장실 가기'에는 3개, 그리고 '나가기'에는 4개의 활동들이 포함되었다. 이러한 결과들과 함께 특이점을 논의하였으며, 마지막에는 연구의 의의와 제한점을 추가하였다.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• 제22권4호
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• pp.377-386
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• 2019

Purpose: Percutaneous liver biopsy (PLB), a diagnostic procedure to identify several hepatobiliary disorders, is considered safe with low incidence of associated complications. While postoperative monitoring guidelines are suggested for adults, selection of procedural recovery time for children remains at the discretion of individual operators. We aim to determine if differences exist in frequency of surgical complications, unplanned admissions, and healthcare cost for children undergoing outpatient PLB for cohorts with same-day vs. overnight observation. Methods: We performed a retrospective cohort study in children 1 month to 17 years of age undergoing ultrasound-guided PLB from January 2009 to August 2017 at a tertiary care, pediatric referral center. Cohorts were defined by postprocedural observation duration: same-day (${\leq}8$ hours) vs. overnight observation. Outcomes included surgical complications, medical interventions, unscheduled hospitalization within 7 days, and total encounter costs. Results: One hundred and twelve children met study criteria of which 18 (16.1%) were assigned to same-day observation. No differences were noted in demographics, anthropometrics, comorbidities, biopsy indications, or preoperative coagulation profiles. No major complications or acute hospitalizations after PLB were observed. Administration of analgesia and fluid boluses were isolated and given within 8 hours. Compared to overnight monitoring, same-day observation accrued less total costs (US $992 less per encounter). Conclusion: Same-day observation after PLB in children appears well-tolerated with only minor interventions and complications observed within 8 hours of procedure. We recommend a targeted risk assessment prior to selection of observation duration. Same-day observation appears an appropriate recovery strategy in otherwise low-risk children undergoing outpatient PLB.

• 대한조선학회논문집
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• 제40권4호
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• pp.16-21
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• 2003

The very large container ships have been built recently and those ships have very small structural rigidity compared with the other conventional ships. As a result, the destruction of ship hull is occurred by the springing including to warping phenomena due to encounter waves. In this study, the solutions of hydrodynamic coefficients are obtained by solving the three dimensional source distribution method and the forward speed Green function representing a translating and pulsating source potential for infinite water depth is used to calculating the integral equation. The vessel is longitudinally divided into various sections and the added mass, wave damping and wave exciting forces of each section is calculated by integrating the dynamic pressures over the mean wetted section surface. The equations for six degree freedom of motions is obtained for each section in the frequency domain and stiffness matrix is calculated by Euler beam theory. The computations are carried out for very large ship and effects of bending and torsional ridigity on the wave frequency and angle are investigated.