• Structural Engineering and Mechanics
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• 제23권1호
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• pp.29-42
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• 2006

This paper describes the design scheme of the three-dimensional structures based on the concept of the cellular automata simulation. The cellular automata simulation is performed according to the local rule. In this paper, the local rule is derived in the mathematical formulation from the optimization problem. The cell density is taken as the design variable. Two objective functions are defined for reducing the total weight of the structure and obtaining the fully stressed structure. The constraint condition is defined for defining the local rule. The penalty function is defined from the objective functions and the constraint condition. Minimization of the penalty function with respect to the design parameter leads to the local rule. The derived rule is applied to the design of the three-dimensional structure first. The final structure can be obtained successfully. However, the computational cost is expensive. So, in order to reduce the computational cost, the material parameters $c_1$ and $c_2$ and the value of the cell rejection criterion (CRC) are changed. The results show that the computational cost depends on the parameters and the CRC value.

• 방송공학회논문지
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• 제26권5호
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• pp.592-598
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• 2021

현 이동통신 시스템은 재난경보 방송을 위하여 CBS 프로토콜을 이용한다. 그러나 CBS 프로토콜 표준은 제한된 텍스트 문자의 전송만을 규정하고 있다. 따라서 국내 문자에 익숙하지 않은 외국인 등은 수신된 메시지를 충분히 이해하기 어려운 단점이 있다. 또한, 현 CBS는 메시지의 글자수 제한으로 자세한 정보를 전송하기 어려운 한계를 가진다. 이러한 어려움을 극복하기 위하여 본 논문에서는 CBS 재난문자 전송시 단말기에서 이미지 정보 와 URL을 표출하는 기법을 제안한다. 이 기법은 5G 이동통신을 위한 CBS의 메시지 구조를 이용한다. 이 메시지 구조를 이용할 경우 CBS 프로토콜은 문자 코딩방식에 관계없이 단말기에서 이미지 정보와 URL을 표출할 수 있음을 보인다.

• Composites Research
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• 제36권3호
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• pp.205-210
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• 2023

본 연구에서는 폼 구조의 효율적인 유효 기계적 물성 및 열전도율 예측을 위한 균질화 데이터 기반 전이학습 프레임워크를 개발하였다. Eshelby 텐서 기반의 평균장 균질화(Mean-field homogenization, MFH)는 타원체 형태의 공동을 포함하는 다공성 구조의 물성을 효율적으로 예측할 수 있지만, 셀룰러(cellular) 폼 구조의 물성은 정확하게 예측하기 어렵다. 한편, 유한요소 균질화(Finite element homogenization, FEH)는 정확성은 높지만 상대적으로 높은 해석 시간을 동반한다. 본 논문에서는 평균장 균질화와 유한요소 균질화의 장점을 결합한 데이터 기반 전이학습 프레임워크(Framework)를 제안하였다. 구체적으로, 대량의 평균장 균질화 데이터를 도출하여 사전학습 모델(Pre-trained model)을 구축하고, 상대적으로 소량의 유한요소 균질화 데이터를 이용하여 미세 조정(Fine-tuning) 하였다. 제안된 프레임워크를 검증하기 위한 수치 예제를 수행하였으며, 해석 정확도를 확인하였다. 본 연구의 결과는 다양한 폼 구조를 가진 재료의 해석에 적용할 수 있을 것으로 기대한다.

• Composites Research
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• 제36권3호
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• pp.173-179
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• 2023

The sandwich structure, consisting of a core and a face sheet, is used for lightweight structural application. Generally, cellular structures like honeycomb, foam, and lattice structures are utilized for the core. Among these, lattice structures have several advantages over other types of structures. In other studies, curved lattice structures were reported to have higher mechanical properties than straight structures by converting shear stresses acting on the structure into compressive stresses. Moreover, the addition of vertical struts can have a positive effect on the mechanical properties of the lattice structure. For the purpose, two lattice structures with Circle Arch (CC) and Circular Arch with a vertical column (CC_C) were studied, which were fabricated by using selective laser sintering was conducted. The result showed that CC_C has dramatic performance improvements in specific strength, modulus, and strain energy density compared to CC, confirming that vertical struts played a significant role in the lattice core. Finite element analysis was employed to determine the cause of the stress behavior of CC and CC_C. This study is expected to help design structurally superior lattice cores and sandwich structures.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.130-135
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• 2007

The mechanical characteristics of three types of core with two-dimensional isotropic patterns-triangular, hexagonal and starcell-were studied in applications to sandwich structures. The Young's modulus and shear modulus were calculated for the three core types in the direction normal to the faces. The compressive buckling strength and shear buckling strength were calculated by modeling each cell wall of the core as a plate under compressive or shear load. To verify this model, tests were conducted on scaled specimens to measures the compressive buckling strength of each core. The bending flexibilities of the three cores were also studied. Compliances for the three cores were measured using biaxial flexural tests. The three isotropic core patterns exhibited distinct characteristics. In the direction normal to the faces, all three cores had the same stiffness. However, the starcell core exhibited high flexibility compared to the other cores, indicating potential for application to curved sandwich structures.

• 대한약학회:학술대회논문집
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• 대한약학회 2002년도 Proceedings of the Convention of the Pharmaceutical Society of Korea Vol.2
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• pp.173-174
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• 2002

Oxidative modification of cellular structures and functions by redox imbalance is the basis of the current oxidative stress hypothesis of aging. The experimental support for this hypothsis has been generated from recent molecular probing on the interrelation between the age-related functional impairments and the pathogenesis. (omitted)

• Molecules and Cells
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• 제27권2호
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• pp.269-269
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• 2009

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.1663-1666
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• 2007

The finite element method is applied to analyze the deformation mechanisms in the closed-cell Al foam under the compression. The modeling of the real cellular structure proceeds with the concept of the reverse engineering. First of all, the small, $10{\times}\;10{\times}\;10mm^3$ sized specimens of the closed-cell Al foam are prepared. The micro focus X-ray CTsystem of SHIMADZU Corp. is used to scan the full structures of the specimens. The scanned structures are converted to the geometric surfaces and solids through the software for 3-D scan data processing, RapidFormTMof INUS Tech. Inc. Then the solid meshes are directly generated on the converted geometric solids for the finite element analysis. The large elastic-plastic deformation and 3-D contact problems for the Al cellular material are considered. The clear and successful analysis for the deformation mechanisms in the closed-cell Al foam is carried out through the comparison of the numerical results in this research with the referred experimental ones.

• Asian Pacific Journal of Cancer Prevention
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• 제16권18호
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• pp.8467-8471
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• 2016

Background: One of the major mechanisms for drug resistance is associated with altered anticancer drug transport, mediated by the human-adenosine triphosphate binding cassette (ABC) transporter superfamily proteins. The overexpression of adenosine triphosphate binding cassette, sub-family B, member 1 (ABCB1) by multidrug-resistant cancer cells is a serious impediment to chemotherapy. In our study we have studied the possibility that structural single-nucleotide polymorphisms (SNP) are the mechanism of ABCB1 overexpression. Materials and Methods: A total of 101 gastric cancer multidrug resistant cases and 100 controls were genotyped with sequence-specific primed PCR (SSP-PCR). Gene expression was evaluated for 70 multidrug resistant cases and 54 controls by real time PCR. The correlation between the two groups was based on secondary structures of RNA predicted by bioinformatics tool. Results: The results of genotyping showed that among 3 studied SNPs, rs28381943 and rs2032586 had significant differences between patient and control groups but there were no differences in the two groups for C3435T. The results of real time PCR showed over-expression of ABCB1 when we compared our data with each of the genotypes in average mode. Prediction of secondary structures in the existence of 2 related SNPs (rs28381943 and rs2032586) showed that the amount of ${\Delta}G$ for original mRNA is higher than the amount of ${\Delta}G$ for the two mentioned SNPs. Conclusions: We have observed that 2 of our studied SNPs (rs283821943 and rs2032586) may elevate the expression of ABCB1 gene, through increase in mRNA stability, while this was not the case for C3435T.

• 대한의생명과학회지
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• 제2권2호
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• pp.159-166
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• 1996

인터루킨-1을 횐쥐의 기관지 내로 투여하였을 때 급성 부종성 폐손상(acute edematous lung injury)이 유발되며, 폐세척액 내 호중구가 증가되고 surfactant의 양도 증가한다. 대식세포는 증가된 surfactant 기인한 탐식작용 활동이 증가하여 세포 내 환상의 구조물들이 증가하나 정상군과 비교하여 형태적으로 세포기관의 구조에서 차이를 보이고 있다. 이러한 세포구성은 세포간 기능상 의 차이를 나타내는 것이며, surfactant의 순환과 연관성이 있을 것으로 사료된다. 본 연구에서 정상 군에 있어서 폐포강 내 대식세포가 환상의 구조물들을 합성하는 형태를 보였으며, 이것은 surfactant의 재합성과 분비작용과 매우 밀접한 연관성이 있음을 보여 주는 것이다.