• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제9권5호
• /
• pp.1840-1855
• /
• 2015

Troubles are often met when traditional active contours extract boundaries of medical images with inhomogeneous bias and various noises. Focusing on such a circumstance, a localized mutual information active contour model is discussed in the paper. By defining neighborhood of each point on the level set, mutual information is introduced to describe the relationship between the zero level set and image field. A driving energy term is then generated by integrating all the information. In addition, an expanding energy and internal energy are designed to regularize the driving energy. Contrary to piecewise constant model, new model has a better command of driving the contours without initialization.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2008년도 추계학술대회B
• /
• pp.2562-2567
• /
• 2008

Jet impingement on a moving plate, which is applicable to cooling of hot metals in a steel-making process, is investigated numerically by solving the Navier-Stokes equations in the liquid and gas phases. The liquid-gas interface or free surface is tracked by a level-set method which is improved by incorporating the ghost fluid approach based on a sharp-interface representation. The computations are made for multiple jets as well as a single jet to compare their flow characteristics. Also, the effects of the nozzle pitch, moving velocity of plate and jet velocity on the interfacial motion and the associated flow and temperature fields.

• Steel and Composite Structures
• /
• 제21권6호
• /
• pp.1389-1410
• /
• 2016

This paper proposes a hybrid of topological derivative-based level set method (LSM) and isogeometric analysis (IGA) for structural topology optimization. In topology optimization a significant drawback of the conventional LSM is that it cannot create new holes in the design domain. In this study, the topological derivative approach is used to create new holes in appropriate places of the design domain, and alleviate the strong dependency of the optimal topology on the initial design. Furthermore, the values of the gradient vector in Hamilton-Jacobi equation in the conventional LSM are replaced with a Delta function. In the topology optimization procedure IGA based on Non-Uniform Rational B-Spline (NURBS) functions is utilized to overcome the drawbacks in the conventional finite element method (FEM) based topology optimization approaches. Several numerical examples are provided to confirm the computational efficiency and robustness of the proposed method in comparison with derivative-based LSM and FEM.

• 인터넷정보학회논문지
• /
• 제13권4호
• /
• pp.53-62
• /
• 2012

객체분할은 영상처리와 컴퓨터비전분야의 상당히 어려운 연구대상이다. 그레이스케일 영상에 대한 영상분할은 매우 많은 방법이 발표되었으며 다양한 영상특징과 처리방법이 제시되었다. 이러한 방법들은 대개 자연상태의 칼라 영상에 적용되기 어렵다. 본 논문에서는 기하학적인 Active Contour 모델의 수정된 형태, 즉 거리정규화레벨셋(distance regularized level set evolution: DRLSE)을 이용한 방법을 제시하여 스피드 함수가 이러한 칼라요소를 반영하도록 하였으며 실험결과 정확성과 시간효율성에 있어서 우수한 결과를 보여주었다.

• 한국해안해양공학회지
• /
• 제5권4호
• /
• pp.263-270
• /
• 1993

일정 경사 해저면을 갖는 해안에 입사한 파가 천수변형을 거치고 쇄파하는 과정에서 발생하는 라디에이션 응력 및 평균수위 변화를 다루었다. 일반적으로 선형파동 이론에 의해 산정된 라디에이션 응력은 쇄파대내 및 그 부근에서 과대 평가되는데, 이것이 평균수위 변동의 계산치와 실험치와의 불일치의 원인이 된다. 본 연구에서는 Svendsen(1984)이 제안한 라디에이션 응력을 수정해서, 수심의 함수로 표시하고, 계산결과를 선형이론, 쇄파의 성분파고 스펙트럼에 기초한 Sawaragi(19梨) 방법 및 기왕의 실험데이타와 비교하였다. 수정된 Svendsen의 방법은 실험치와 비교적 양호한 일치를 보여 주었다.

• 대한조선학회논문집
• /
• 제45권2호
• /
• pp.109-123
• /
• 2008

The present paper presents the CFD result for a beam wave test case. An ONR tumblehome ship model with bilge keels is used. The beam wave test is for zero forward speed and roll and heave 2DOF with wave slope $a_k=0.156$ and wavelength ${\lambda}=1.12L_{PP}$, with $L_{PP}$ the ship length. The problems is solved numerically with an unsteady Reynolds averaged Navier-Stokes approach. The free surface flow is computed using a single-phase level-set method and the motions in each time step are integrated using a predictor-corrector iteration approach which uses dynamic overset grids moving with relative ship motion. The predicted CFD results for motions and forces are compared with experimental data, showing a reasonable agreement.

• 한국방송∙미디어공학회:학술대회논문집
• /
• 한국방송공학회 2009년도 IWAIT
• /
• pp.28-31
• /
• 2009

In this paper, a new approach for solid texture synthesis from input volume data is presented. In the pre-process, feature vectors and a similarity set were constructed for input volume data. The feature vectors were used to construct neighboring vectors for more accurate neighborhood matching. The similarity set which recorded 3 candidates for each voxel helped more effective neighborhood matching. In the synthesis process, the pyramid synthesis method was used to synthesize solid textures from coarse to fine level. The results of the proposed approach were satisfactory.

• Nuclear Engineering and Technology
• /
• 제56권4호
• /
• pp.1225-1233
• /
• 2024

Level 3 probabilistic safety assessment (PSA) is performed to calculate radionuclide concentrations and exposure dose resulting from nuclear power plant accidents. To calculate the external exposure dose from the released radioactive materials, the radionuclide concentrations are multiplied by two factors of dose coefficient and a finite cloud dose correction factor (FCDCF), and the obtained values are summed. This indicates that a standard set of FCDCFs is required for external exposure dose calculations. To calculate a standard set of FCDCFs, the effective distance from the release point to the receptor along the wind direction should be predetermined. The TID-24190 document published in 1968 provides equations to calculate FCDCFs and the resultant standard set of FCDCFs. However, it does not provide any explanation on the effective distance required to calculate the standard set of FCDCFs. In 2021, Sandia National Laboratories (SNLs) proposed a method to predetermine finite effective distances depending on the atmospheric stability classes A to F, which results in six standard sets of FCDCFs. Meanwhile, independently of the SNLs, the authors of this paper discovered that an infinite effective distance assumption is a very reasonable approach to calculate one standard set of FCDCFs, and they implemented it into the multi-unit radiological consequence calculator (MURCC) code, which is a post-processor of the level 3 PSA codes. This paper calculates and compares short- and long-range FCDCFs calculated using the TID-24190, SNLs method, and MURCC method, and explains the strength of the MURCC method over the SNLs method. Although six standard sets of FCDCFs are required by the SNLs method, one standard sets of FCDCFs are sufficient by the MURCC method. Additionally, the use of the MURCC method and its resultant FCDCFs for level 3 PSA was strongly recommended.

• The Journal of Korean Physical Therapy
• /
• 제26권5호
• /
• pp.351-357
• /
• 2014

Purpose: The purpose of this study was to investigate level of functioning in patients with stroke using Modified Bathel Index (MBI), World Health Organization Disability Assessment Schedule 2.0 (WHODAS 2.0), and ICF core-set for stroke. Methods: Sixty-four patients with stroke were recruited for this study from nine medical institutes. The ICF core-set for stroke, WHODAS 2.0, and MBI were used to collect subjects' functional levels. ICF core-set was employed here as a standard frame to observe multi-dimension of functioning, that is physiological bodily function, activity and participation (AP) in daily life, and current environmental factors (EF) in patients with stroke. WHODAS 2.0 and MBI were also used in order to have a specific functioning level for subjects. The linkage of each item in WHODAS 2.0 and MBI into the ICF core-set for stroke was examined. Pearson correlation coefficient was used for analysis of their relationships. Results: Functioning level of participants showed moderate resulting from MBI and WHODAS 2.0 ($73.48{\pm}22.27$ and $35.55{\pm}12.53$, respectively). Strong relationship was observed between ICF core-set and WHODAS 2.0, and with MBI. Each item of disability scales was obtained its linkage into ICF in the domain of AP. However, lack of correlation between MBI and ICF in the domain of EF was found due to absence of related factors. Conclusion: MBI was found to be linked mainly into ICF in the domain of AP and to have limited linkage into EF. Therefore, it should be suggested that the ICF concept frame should be used as a multi-dimensional approach to patients with stroke.

• 경영과학
• /
• 제20권2호
• /
• pp.95-111
• /
• 2003

The standard issue in the information and telecommunication industry is increasingly important with the rapid development of technology. This paper proposes an index model which can measure the degree of standardization in the Korean information and telecommunication field. We first classified ICT sector into 14 sub-sectors. Then for each sub-sector, we considered a set of important determinants to measure the level of standardization, and constructed a linear equation using this set of determinants. Finally we estimated the relative degree of importance of each determinant using the AHP methodology. The proposed model found that overall level of standardization in the Korean ICT industry is relatively low, and ‘IMT-2000 technology’ and ‘computer network technology’ among 14 sub-sectors are highly standardized sub-sectors. The validity of the proposed model was also partially proved using two different methods, holistic and historical approach.