• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.358-358
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• 2010

Ion beam bombardment at low energy forms nanosize patterns such as ripples, dots or wrinkles on the surface of polymers in ambient temperature and pressure. It has been known that the ion beam can alter the polymer surface that induces skins stiffer or the density higher by higher compressive stress or strain energies associated with chain scissions and crosslinks of the polymer. Atomic scale structure evolution in polymers is essential to understand a stress generation mechanism during the ion beam bombardment, which governs the nanoscale surface structure evolution. In this work, Molecular Dynamics (MD) simulations are employed to characterize the phenomenon occurred in bombardment between the ion beam and polymers that forms nanosize patterns. We investigate the structure evolution of Low Density Polyethylene (LDPE) at 300 K as the polymer is bombarded with Argon ions having various kinetic energies ranging from 100 eV to 1 KeV with 50 eV intervals having the fluence of $1.45\;{\times}\;1014 #/cm2$. These simulations use the Reactive Force Field (ReaxFF), which can mimic chemical covalent bonds and includes van der Waals potentials for describing the intermolecular interactions. The results show the details of the structural evolution of LDPE by the low energy Ar ion bombardment. Analyses through kinetic and potential energy, number of crosslinks and chain scissions, level of local densification and motions of atoms support that the residual strain energies on the surface is strongly associated with the number of crosslinks or scissored chains. Also, we could find an optimal Ar ion beam energy to make crosslinks well.

• 한국재료학회지
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• 제4권7호
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• pp.792-797
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• 1994

6-31G $\ast$ $\ast$ basis set을 이용한 ab initio 양자역학적 방법에 의하여 2,4,6- trifluoroheptane구조를 구함으로서 syndiotactic isoregic PVF결정의 force field를 유도하였다. 또 그 결과를 PVF의 structure parameter및 elastic constant를 계산하는데 응용하였다. 그 결과 cell parameter는 각각 a(5.205$\AA$: chain axis), b(8.457 $\AA$) 및 c(4.621 $\AA$)로 나타났으며 X-ray data(5.04$\AA$, 8.57$\AA$, 및 4.95$\AA$)결과와 비교적 잘 일치함을 알 수 있었다. Defect 비존재하에서의 syndiotactic PVF결정의 Young's 모듈러스 계산값은 267Gpa로 나타났으며, polyvinylideme fluoride(277-293 GPa)및 polyethylene(264-337 GPa)결정의 경우와 비슷한 수준으로 나타났다. 또한 optimum geometry에서 얻어진 bulk modulus값은 experimental geometry 에서 얻어진 값보다 두배의 차이를 보였으며, 이것은 geometry 에 따른 elastic compliance constant(특히 $S_{33}$인자)가 크게 달라지기 때문인 것으로 나타났다.

• Nuclear Engineering and Technology
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• 제42권6호
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• pp.620-635
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• 2010

In this paper we describe current activities on the project Multi-Scale Modeling and Analysis of convective boiling (MSMA), conducted jointly by the Paul Scherrer Institute (PSI) and the Swiss Nuclear Utilities (Swissnuclear). The long-term aim of the MSMA project is to formulate improved closure laws for Computational Fluid Dynamics (CFD) simulations for prediction of convective boiling and eventually of the Critical Heat Flux (CHF). As boiling is controlled by the competition of numerous phenomena at various length and time scales, a multi-scale approach is employed to tackle the problem at different scales. In the MSMA project, the scales on which we focus range from the CFD scale (macro-scale), bubble size scale (meso-scale), liquid micro-layer and triple interline scale (micro-scale), and molecular scale (nano-scale). The current focus of the project is on micro- and meso-scales modeling. The numerical framework comprises a highly efficient, parallel DNS solver, the PSI-BOIL code. The code has incorporated an Immersed Boundary Method (IBM) to tackle complex geometries. For simulation of meso-scales (bubbles), we use the Constrained Interpolation Profile method: Conservative Semi-Lagrangian $2^{nd}$ order (CIP-CSL2). The phase change is described either by applying conventional jump conditions at the interface, or by using the Phase Field (PF) approach. In this work, we present selected results for flows in complex geometry using the IBM, selected bubbly flow simulations using the CIP-CSL2 method and results for phase change using the PF approach. In the subsequent stage of the project, the importance of effects of nano-scale processes on the global boiling heat transfer will be evaluated. To validate the models, more experimental information will be needed in the future, so it is expected that the MSMA project will become the seed for a long-term, combined theoretical and experimental program.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권7호
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• pp.3494-3510
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• 2019

Wireless sensor networks encounter energy saving as a major issue as the sensor nodes having no rechargeable batteries and also the resources are limited. Clustering of sensors play a pivotal role in energy saving of the deployed sensor nodes. However, in the cluster based wireless sensor network, the cluster heads tend to consume more energy for additional functions such as reception of data, aggregation and transmission of the received data to the base station. So, careful selection of cluster head and formation of cluster plays vital role in energy conservation and enhancement of lifetime of the wireless sensor networks. This study proposes a new mutation chemical reaction optimization (MCRO) which is an algorithm based energy efficient clustering protocol termed as MCRO-ECP, for wireless sensor networks. The proposed protocol is extensively developed with effective methods such as potential energy function and molecular structure encoding for cluster head selection and cluster formation. While developing potential functions for energy conservation, the following parameters are taken into account: neighbor node distance, base station distance, ratio of energy, intra-cluster distance, and CH node degree to make the MCRO-ECP protocol to be potential energy conserver. The proposed protocol is studied extensively and tested elaborately on NS2.35 Simulator under various senarios like varying the number of sensor nodes and CHs. A comparative study between the simulation results derived from the proposed MCRO-ECP protocol and the results of the already existing protocol, shows that MCRO-ECP protocol produces significantly better results in energy conservation, increase network life time, packets received by the BS and the convergence rate.

• Journal of Microbiology and Biotechnology
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• 제29권9호
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• pp.1375-1382
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• 2019

Phenylalanine hydroxylase from Chromobacterium violaceum (CvPAH) is a monomeric enzyme that converts phenylalanine to tyrosine. It shares high amino acid identity and similar structure with a subunit of human phenylalanine hydroxylase that is a tetramer, resulting in the latent application in medications. In this study, semirational design was applied to CvPAH to improve the catalytic ability based on molecular dynamics simulation analyses. Four N-terminal truncated variants and one single point variant were constructed and characterized. The D267P variant showed a 2.1-fold increased thermal stability compared to the wild type, but lower specific activity was noted compared with the wild type. The specific activity of all truncated variants was a greater than 25% increase compared to the wild type, and these variants showed similar or slightly decreased thermostability with the exception of the $N-{\Delta}9$ variant. Notably, the $N-{\Delta}9$ variant exhibited a 1.2-fold increased specific activity, a 1.3-fold increased thermostability and considerably increased catalytic activity under the neutral environment compared with the wild type. These properties of the $N-{\Delta}9$ variant could advance medical and pharmaceutical applications of CvPAH. Our findings indicate that the N-terminus might modulate substrate binding, and are directives for further modification and functional research of PAH and other enzymes.

• 한국정보전자통신기술학회논문지
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• 제12권1호
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• pp.37-42
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• 2019

본 논문에서는 부호 길이 내에서 1개의 오류를 정정할 수 있는 해밍 부호(Hamming code)에 대해 2 개의 오류를 정정할 수 있는 신드롬 복호 기법을 제안하였다. 본 논문에서 제안한 복호 기법은 복호 복잡도를 거의 증가시키지 않으면서도 다중 오류를 정정함으로서 복호 복잡도 대비 오율 성능을 크게 개선할 수 있는 장점을 갖는다. 본 논문에서 제안한 복호 기법은 IoT 기기들 간의 통신이나 분자 통신과 같이 부/복호기에서 에너지의 사용이 극히 제한된 환경에서 부 복호기의 에너지 사용이 적으면서도 우수한 오율 성능이 요구되는 경우에 적합하다. 본 논문에서 제안한 복호 기법이 적용된 해밍 부호의 오율 성능이 개선되었음을 보이기 위해 BPSK 변조 방식과 AWGN 채널 환경에서 부호 길이가 짧은 다수의 해밍 부호에 대해 시뮬레이션을 수행하였으며, 수행 결과 해밍 부호의 부호 길이에 무관하게 제안한 복호 방식은 기존 복호 방식에 비해 약 1.1[dB] ~ 1.2[dB] 정도의 성능 개선을 확인할 수 있었다.

• 한국콘텐츠학회논문지
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• 제20권12호
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• pp.537-546
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• 2020

본 연구에서는 오염물 사고에 대한 신속한 대응을 위하여 입자 분산 모형을 개발 및 개선하고 병렬 프로그램을 적용한 모의 속도 증가와 그 분석을 통하여 속도개선 결과를 평가하였다. 개발된 모형은 전단류 분산이론을 따르면서 수평 혼합 과정은 전단이송, 연직 혼합 과정은 연직배열 알고리즘을 이용한 난류 및 입자 확산을 구현하였다. 오염사고에 신속하게 대응하기 위해 모형 속도 개선을 위하여 OpenMP를 활용한 병렬 프로그래밍으로 멀티코어 적용 알고리즘을 적용하였다. 병렬 프로그래밍 적용 결과, 가상 사행수로에서 기준 소요시간 내로 모의가 가능한 입자 및 활용 코어 개수의 관계를 도출할 수 있었다. 이 연구 결과로 신속한 수질 오염사고 사고대응을 위한 적절한 모의 조건을 구성할 수 있게 되어 모형의 활용성을 증대할 수 있었다.

• Steel and Composite Structures
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• 제42권6호
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• pp.779-789
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• 2022

This work presents a non-linear cylindrical bending analysis of functionally graded plate reinforced by single-walled carbon nanotubes (SWCNTs) in thermal environment using a simple integral higher-order shear deformation theory (HSDT). This theory does not require shear correction factors and the transverse shear stresses vary parabolically through the thickness. The material properties of SWCNTs are assumed to be temperature-dependent and are obtained from molecular dynamics simulations. The material properties of functionally graded carbon nanotube-reinforced composites (FG-CNTCRs) are considered to be graded in the thickness direction, and are estimated through a micromechanical model. The non-linear strain-displacement relations in the Von Karman sense are used to study the effect of geometric non-linearity and the solution is obtained by minimization of the total potential energy. The numerical illustrations concern the nonlinear bending response of FG-CNTRC plates under different sets of thermal environmental conditions, from which results for uniformly distributed CNTRC plates are obtained as benchmarks.

• 마이크로전자및패키징학회지
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• 제29권4호
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• pp.55-61
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• 2022

다중 암의 동시 진단 기술에 대한 관심이 전 세계적으로 증가하는 추세이며, 진단 난이도를 낮추기 위해 혈액과 같은 미량의 바이오 유체를 이용하여 질병을 진단하는 미세 유체 소자 기반의 액체 생검 기술이 연구되고 있다. 바이오 유체를 이용하여 형광 영상 등을 통해 분석물질의 농도를 측정하는 광학적 바이오 센싱에 있어 민감도를 향상시키기 위한 기술개발이 필요하다. 본 논문에서는 모세관력에 의한 자가구동 기반의 마이크로 채널의 기하학적 구조와 미세 유체 현상만으로 수동적 자기 혈장 분리 기술과 유체 혼합을 통한 분자 인식 활성화 기능을 구현하는 형광 다중 암 진단 센서 플랫폼 구조를 제안하고 설계하였다. 설계된 센서의 혈장 분리부의 성능에 영향을 미치는 파라미터를 확인하기 위해 채널의 수력학적 직경과 종횡비, 유체의 점도를 변수로 설정하여 딘 와류 형성 여부를 시뮬레이션을 통해 확인하였고 최적의 센서 플랫폼 구조를 제시하였다.

• Genomics & Informatics
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• 제21권3호
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• pp.30.1-30.13
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• 2023

Ephs belong to the largest family of receptor tyrosine kinase and are highly conserved both sequentially and structurally. The structural organization of Eph is similar to other receptor tyrosine kinases; constituting the extracellular ligand binding domain, a fibronectin domain followed by intracellular juxtamembrane kinase, and SAM domain. Eph binds to respective ephrin ligand, through the ligand binding domain and forms a tetrameric complex to activate the kinase domain. Eph-ephrin regulates many downstream pathways that lead to physiological events such as cell migration, proliferation, and growth. Therefore, considering the importance of Eph-ephrin class of protein in tumorigenesis, 7,620 clinically reported missense mutations belonging to the class of variables of unknown significance were retrieved from cBioPortal and evaluated for pathogenicity. Thirty-two mutations predicted to be pathogenic using SIFT, Polyphen-2, PROVEAN, SNPs&GO, PMut, iSTABLE, and PremPS in-silico tools were found located either in critical functional regions or encompassing interactions at the binding interface of Eph-ephrin. However, seven were reported in nonsmall cell lung cancer (NSCLC). Considering the relevance of receptor tyrosine kinases and Eph in NSCLC, these seven mutations were assessed for change in the folding pattern using molecular dynamic simulation. Structural alterations, stability, flexibility, compactness, and solvent-exposed area was observed in EphA3 Trp790Cys, EphA7 Leu749Phe, EphB1 Gly685Cys, EphB4 Val748Ala, and Ephrin A2 Trp112Cys. Hence, it can be concluded that the evaluated mutations have potential to alter the folding pattern and thus can be further validated by in-vitro, structural and in-vivo studies for clinical management.