• Journal of the KSME
• /
• v.25 no.6
• /
• pp.497-501
• /
• 1985

연속체역학은 고전역학을 종합하여 더 합리적인 체계로 정리 발전시키려는 금세기 후반에 집중된 노력의 결정으로 볼 수 있다(1,2). 연속체의 역학적 거동에 관한 기초적 개요를 쉽게 설명하고 관련문현을 제시하여 일반기술자의 관심을 돕고저 한다(연속체역학의 우리 용어들이 정립되지 않은 것은 필자 임의로 선택하였으니 양해를 바라며, 개요의 부족함은 기초적 문헌(4)으로 쉽게 보충되도록 유의하였다)

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.14 no.4
• /
• pp.321-336
• /
• 2012

The shear behavior at the particle/surface interface such as rock joint can determine the mechanical behavior of whole structure. Therefore, a fundamental understanding of the mechanisms governing its behavior and accurately estimation of the interface strength is essential. In this paper, PFC, a numerical analysis program of discrete element method was used to investigate the effects of the surface roughness crushing on interface strength. The surface roughness was characterized by smooth, intermediate, and rough surface, respectively. Particle shape was classified into one ball model of circular shape and 3 ball model of triangular shape. The surface shape was modelled by wall model of non-crushing surface and ball model of crushing surface. The results showed that as the bonding strength of ball model decreases, lower interface strength is induced. After the surface roughness crushing was occurred, the interface strength tended to converge and higher bonding strength induced lower surface roughness crushing. Higher friction angle was induced in wall model and higher surface roughness induced the higher friction angle. From these findings, it is verified that the surface roughness and surface roughness crushing effect on the particle/surface interface shear behavior.

• Proceeding of EDISON Challenge
• /
• 2017.03a
• /
• pp.333-339
• /
• 2017

최근에는 항공기의 임무 형태나 주위 환경에 따라 변할 수 있는 passive morphing airfoil에 대한 연구가 활발히 이루어지고 있다. 하지만 복잡한 모델링, 실험 과정 및 긴 해석 시간 때문에 아직 여러 chiral 구조를 체계적으로 비교하지 못 하고 있다. 본 논문에서는 이러한 chiral meso structure 중 하나인 Anti-Tetra Chiral 구조를 Hooke's law에 기반을 두어 등가 물성치를 구해보고, 사각형 모양의 연속체 요소로 등가 모델링을 하였다. 그 후, airfoil 내부에 연속체 요소를 직접 적용하여 실제 모델링한 경우와 비교해 본 결과 경향성 파악에 충분한 오차 범위를 얻을 수 있었다. 이를 통해 여러종류의 Chiral meso structure과 기하학적 변수를 적용한 에어포일을 효율적으로 해석할 수 있음을 제시할 수 있다.

• Proceedings of the KSR Conference
• /
• 2006.11b
• /
• pp.31-34
• /
• 2006

A new continuum damage theory (CDT) has been proposed by Lee et al. (1996) based on the SEEP. The CDT has the apparent advantage over the other related theories because the complete constitutive law can be readily derived by simply replacing the virgin elastic stiffness with the effective orthotropic elastic stiffness obtained by using the proposed continuum damage theory. In this paper, the CDT is evaluated by the numerical experiment comparing the mode shapes and natural frequencies of a square plate containing a small line-through crack with those of the same plate with a damaged site replaced with the effective orthotropic elastic stiffness computed by using the CDT.

• Computational Structural Engineering
• /
• v.3 no.4
• /
• pp.105-112
• /
• 1990

A rational and straightforward method is introduced for developing continuum models of large platelike periodic lattice structures based on energy equivalence, The procedure for developing continuum models involves using existing finite element matrices in calculating strain and kinetic energies of a repeating cell. The equivalent continuum plate properties are obtained from the direct comparison of the reduced stiffness and mass matrices for continuum and lattice plates. Numerical results prove that the method developed in this paper shows very good agreement with other well-recognized methods.

• Tunnel and Underground Space
• /
• v.11 no.2
• /
• pp.156-166
• /
• 2001

A stochastic continuum(SC) modeling technique was developed to simulate the groundwater flow pathway in fractured rocks. This model was developed to overcome the disadvantageous points of discrete fracture network(DFN) modes which has the limitation of fracture numbers. Besides, SC model is able to perform probabilistic analysis and to simulate the conductive groundwater pathway as discrete fracture network model. The SC model was formulated based on the discrete fracture network(DFN) model. The spatial distribution of permeability in the stochastic continuum model was defined by the probability distribution and variogram functions defined from the permeabilities of subdivided smaller blocks of the DFN model. The analysis of groundwater travel time was performed to show the consistency between DFN and SC models by the numerical experiment. It was found that the stochastic continuum modes was an appropriate way to provide the probability density distribution of groundwater velocity which is required for the probabilistic safety assessment of a radioactive waste disposal facility.

• Tunnel and Underground Space
• /
• v.27 no.5
• /
• pp.303-311
• /
• 2017

The correlation analysis between the results obtained from DFN flow model and equivalent continuum flow model were conducted on total of 72 DFN blocks having various fracture geometry and domain size. A strong linear relation seems to exist between the two approaches under condition that normalized relative error for continuum behavior (ER) is less than 0.2, and the results from both methods are found to almost identical. To explore the field applicability of equivalent continuum flow model in DFN media, a total of 48 numerical schemes related to inflow of underground circular openings were implemented under various DFN configurations. The equivalent continuum flow model in DFN media with a constant hydraulic aperture was evaluated as valid. However, as the anisotropy increases due to variation of the hydraulic aperture, the results are likely to be overestimated compare to the DFN flow model.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2000.11a
• /
• pp.3-3
• /
• 2000

저추진력 추력기라는 것은 추력이 수 N 정도, 노즐출구직경이 수 mm 정도의 소형추력기를 의미하며, 주로 인공위성을 비롯한 우주 비행체의 자세제어, 궤도천이 등의 목적을 위해 사용된다. 따라서, 저추진력 추력기의 일반적인 작동환경은 연속체 영역, 천이영역(transition flow regime), 희박영역(rarefied flow regime)을 모두 포함하므로, 기존의 연속체 유체역학에서 사용되는 Navier-Stokes 방정식을 사용할 수 없고, 분자들의 미시적인 움직임과 내부 에너지 분포를 고려한 Boltzmann 방정식을 이용한 해석을 수행하여야 한다.(중략)

• Annual Conference on Human and Language Technology
• /
• 2012.10a
• /
• pp.185-190
• /
• 2012

본 논문은 동아, 조선, 중앙, 한겨레 신문의 2009년 신문 사설의 제목과 본문에서 나타나는 n-gram에 대한 논의이다. 구체적으로 자주 출현하는 단어들의 연속 단위 3~6개의 형태소를 추출하여 신문 사설에서 나타난 고빈도 형태소 연속체를 살펴본다. 또한 이들을 기사문에서 추출한 패턴과 로그공산비로 비교하여 신문 사설에서 더 특징적인 의미로 사용되는 어휘들을 살펴본다. 그 결과, 사설 본문에서는 3-gram은 '아야 한다'. 4-gram은 'ㄹ 것이다', 5-gram은 'ㄹ 수밖에 없다', 6-gram은 '아야 할 것이다' 등이, 사설 제목은 '것인가, 안 된다'가 하나의 용어처럼 사용되고 있었다. 이러한 형태소 연속체를 살펴봄으로써, 신문사설의 텍스트 특징과 정형적인 표현에 대해서 살펴볼 수 있다.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.41 no.6
• /
• pp.429-434
• /
• 2017

A molecular-continuum hybrid method was developed to simulate microscale and nanoscale fluids where continuum fluidics cannot be used to predict Couette flow. Molecular dynamics simulation is used near the solid surface where the flow cannot be predicted by continuum fluidics, and Navier-Stokes equations are used in the other regions. Numerical simulation of Couette flow was performed using the hybrid method to investigate the effect of solid-liquid interaction and surface roughness in a nanochannel. It was found that the solid-liquid interaction and surface roughness influence the boundary condition. When the surface energy is low, slippage occurs near the solid surface, and the magnitude of slippage decreases with increase in surface energy. When the surface energy is high, a locking boundary condition is formed. The roughness disturbs slippage near the solid surface and promotes the locking boundary condition.