• EDISON SW 활용 경진대회 논문집
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• 제4회(2015년)
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• pp.234-238
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• 2015

When we use a Finite Elements Method (FEM) to solve a linear static analysis problem, number of elements need to be sufficiently small for convergence of the solution. If we analysis a part, whose curvature is varying heavily, we face to determine how small the elements size is, because the calculated stress is increased as the elements are smaller. In this case, we need to analysis with mesh insensitive method, stress linearization. We can get a solution that is not varying with the elements size if the size is smaller than a certain level. In this paper, we evaluate a pressure vessel having geometrical discontinuities using stress linearization. First, we analysis the vessel with global model, including all part of the vessel, using large shell elements. Second, we analysis the local part of the vessel, which is the small part occurring maximum stress, using small continuum elements. Last, we evaluate the safety of the pressure vessel according to the ASME Sec. VIII Div 2.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2012년도 제38회 춘계학술대회논문집
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• pp.403-407
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• 2012

본 연구의 목적은 최적화 해석 기법을 이용하여 복합재 압력용기의 스커트 치수를 도출하는 것이다. 복합재 압력용기의 스커트 최적화 해석은 부분문제 근사법(sub-problem approximation method) 알고리즘을 사용하였으며, APDL(ANSYS Parametric Design Language)을 이용하여 해석의 모든 과정을 일괄처리(batch processing)하였다. 설계변수로는 압력용기 스커트 부위의 두께와 길이를 선정하였으며, 내압에 의해 발생하는 변위와 무게를 각각 목적함수로 하여 최적화 해석을 통해 최적의 스커트 치수를 도출하였다. 그 결과 복합재 압력용기의 스커트 무게를 최대 4.38% 절감할 수 있었다.

• 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.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 춘계학술대회논문집
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• pp.743-749
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• 2005

In this work, two dynamic absorbers are introduced and designed to reduce the vibration of the large-size pressure vessel of a reactor for a petrochemical plant. The vibration modes and harmonic responses of the vessel are firstly analyzed by the finite element method. On the basis of the analyzed results, two dynamic absorbers are designed by a simple design theory. Furthermore, an optimization process is executed and an optimal design of the dynamic absorber is obtained to improve performance and structural safety of the vessel. As a result, the maximum displacement and stress of the vessel is decreased about 85% and 65% respectively, the design criteria being satisfied.

• 한국소음진동공학회논문집
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• 제15권5호
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• pp.612-619
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• 2005

In this work. two dynamic absorbers are introduced and designed to reduce the vibration of the large-size pressure vessel of a reactor for a petrochemical plant. The vibration modes and harmonic responses of the vessel are firstly analyzed by the finite element method. On the basis of the analyzed results, two dynamic absorbers are designed by a simple design theory. Furthermore, an optimization process is executed and an optimal design of the dynamic absorber is obtained to improve performance and structural safety of the vessel. As a result, the maximum displacement and stress of the vessel is decreased about $85\%$ and $65\%$ respectively, the design criteria being satisfied.

• 한국항해항만학회지
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• 제38권6호
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• pp.689-694
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• 2014

The Korean government has introduced and enforced maritime traffic safety assessment to secure traffic safety since 2010. The maritime traffic safety assessment is needed by law to design a new port or modify an existing one. According to Korea Maritime Safety Act, in the assessment the propriety of marine traffic system consists of the safety of channel transit and berthing/unberthing maneuver, safety of mooring, and safety of marine traffic flow. The safety of channel transit and berthing/unberthing maneuver can be evaluated only by ship-handling simulation. The ship-handling simulation is carried out by sea pilots working with the port concerned. The vessel's proximity measure is an important factor to evaluate traffic safety. The proximity measure is composed of vessel's closest distance to channel boundary and probability of grounding/collision. What is more, the probability of grounding becomes important. According to central limit theorem, a sample has a normal distribution on condition that its size is more than 30. However, more than 30 simulation runs bring about the increase of assessment period and difficulty of employing sea pilots. Therefore this paper is to find out minimum sample size for evaluating vessel's proximity. First sample sets of size of 3, 5, 7, 9 etc. are selected randomly on the basis of normal distribution. And then KS test for goodness of fit and t-test for confidence interval are applied to each sample set. Finally this paper decides the minimum sample size. As a result this paper suggests the minimum sample size of 5, that is, the simulation of more than five times.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.929-933
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• 2003

Internal defects of thin pressure vessel used in the power plants or the chemical plants may be created and grow due to corrosion or creep fatigue to reduce the strength and cause critical failure during operation. Therefore it is very important to detect this defect at the early stage. For this purpose, non-destructive, non-contact and highly sensitive method should be considered for on-line application. In this paper, a laser shearographic interferometer is applied to inspect circular defects and notch defects existed inside of thin pressure vessel under the presence of pressure up to 3 times of atmospheric pressure. The influences of the defect shape and size as well as the internal pressure to the characteristic pattern in the shearography fringe are investigated, and the quantitative evaluation of the defect size is tried. Also the experimental results are compared with the destructive test results to show the applicability of this method to the quantitative evaluation of internal defects in the thin pressure vessel.

• 한국인터넷방송통신학회논문지
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• 제16권6호
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• pp.119-123
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• 2016

연안에는 많은 배들이 운항을 하고 있어 사고의 위험에 노출되어 있다. 특히 안전 장비를 구비하지 않은 소형 선박은 다양한 원인에 의한 선박 상태에 따른 사고, 그리고 주변 선박 및 물체와의 충돌과 같은 해양사고에 무방비 상태에 놓여있다. 따라서 이와 같은 상황을 저렴한 장비를 통하여 해결하는 것이 필요하다. 이를 위하여 본 논문에서는 스마트폰을 이용하여 선박 자체 움직임을 감지할 수 있는 기능을 구현하였다. 움직임이 정해진 임계값을 넘어선 경우, 이 기능은 현재 상황이 이 선박에 위험하다고 판단하고, 이 상황을 선박에 있는 스마프폰 소유자 및 제어 센터로 이상황을 알린다. 이를 통하여 안전 장비가 거의 장착되어 있지 않은 어선, 여객선, 그리고 레저선박과 같은 소형 선박에 적용되어 선박의 안전 항해를 향상시킬 수 있다.

• Current Optics and Photonics
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• 제3권1호
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• pp.54-65
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• 2019

To develop a biomarker predicting tumor treatment efficacy is helpful to reduce time, medical expenditure, and efforts in oncology therapy. In clinics, microvessel density using immunohistochemistry has been proposed as an indicator that correlates with both tumor size and metastasis of cancer. In the preclinical study, we hypothesized that vascular morphometrics using optical coherence tomography angiography (OCTA) could be potential indicators to estimate the treatment efficacy of breast cancer. To verify this hypothesis, a 13762-MAT-B-III rat breast tumor was grown in a dorsal skinfold window chamber which was applied to a nude mouse, and the change in vascular morphology was longitudinally monitored during tumor growth and metronomic cyclophosphamide treatment. Based on the daily OCTA maximum intensity projection map, multiple vessel parameters (vessel skeleton density, vessel diameter index, fractal dimension, and lacunarity) were compared with the tumor size in no tumor, treated tumor, and untreated tumor cases. Although each case has only one animal, we found that the vessel skeleton density (VSD), vessel diameter index and fractal dimension (FD) tended to be positively correlated with tumor size while lacunarity showed a partially negative correlation. Moreover, we observed that the changes in the VSD and FD are prior to the morphological change of the tumor. This feasibility study would be helpful in evaluating the tumor vascular response to treatment in preclinical settings.

• 한국자원식물학회:학술대회논문집
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• 한국자원식물학회 2020년도 춘계학술대회
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• pp.36-36
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• 2020

Symplocos Jacq. including about 350 species is the sole isolated genus of the family Symplocaceae. Despite poorly documented species delimitation and unresolved taxonomic nomenclature four species of Symplocos (S. coreana, S purnifolia, S sawafutagi, and S. tanakana) have been described in Korea. In this study, we carried the comparative wood anatomy of all the four species of Korean Symplocos to understand the wood anatomical variations within these four species. The result of this study indicated that Korean Symplocos are comparatively indistinguishable in terms of their qualitative wood features except for exclusively uniseriate rays present in S. purnifolia instead of uni- to- multiseriate in other three species. However, discrepancies are observed in quantitative wood variables such as vessel density, vessel size, and ray density. The vessel density of S. purnifolia (highest among the four species) is more than two times higher than the S. sawafutagi (lowest among the four species) and S. tanakana. On the other hand, vessel size is likewise reverse to the vessel number relationships i. e. vessel circumference and diameter in both planes of S. sawafutagi and S. tanakana is almost twice a larger than S. purnifolia. Interestingly, S. coreana remains in between of these two groups in terms of vessel features and closer to S. purnifolia in terms of ray density. The cluster analysis based on the paired group (UPGMA) algorithm using the Euclidean similarity index clearly differentiates S. purnifolia from the rest of the taxa representing the first isolated clade of the tree.