• Advances in aircraft and spacecraft science
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• 제9권5호
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• pp.377-400
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• 2022

The aim of this work is a numerical comparison (FEM) between lattice pyramidal-core panel and honeycomb core panel for different core thicknesses. By evaluating the mid-span deflection, the shear rigidity and the shear modulus for both core types and different core thicknesses, it is possible to define which core type has got the best mechanical behaviour for each thickness and the evolution of that behaviour as far as the thickness increases. Since a specific base geometry has been used for the lattice pyramidal core, the comparison gives us the opportunity to investigate the unit cell strut angle giving the higher mechanical properties. The presented work considers a detailed FEM modelling of a standard 3-point bending test (ASTM C393/C393M Standard Practice). Detailed FEM modelling addresses to detailed discretization of cores by means of beam elements for lattice core and shell elements for honeycomb core. Facings, instead, have been modelled by using shell elements for both sandwich panels. On lattice core structure, elements of core and facings are directly connected, to better simulate the additive manufacturing process. Otherwise, an MPC-based constraint between facings and core has been used for honeycomb core structure. Both sandwich panels are entirely built of Aluminium alloy. Prior to compare the two models, the FEM sandwich panel model with lattice pyramidal core needs to be validated with 3-point bending test experimental results, in order to ensure a good reliability of the FEM approach and of the comparison. Furthermore, the analytical validation has been performed according to Allen's theory. The FEM analysis is linear static with an increasing midspan load ranging from 50N up to 500N.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.859-862
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• 2002

The Core Support Barrel (CSB) is a major component of Reactor Internals, and is designed to support and protect the Reactor Core. In this study, Reactor Core, Core Shroud and CSB were simplified to coaxial cylinders and then the offset of Reactor Core & Core Shroud to the dynamic characteristic of CSB was analyzed. For the beam modes, natural frequencies of the cantilevered cylinder are compared with those of the cantilevered beam. And it was found out that shear modulus must be used correctly to convert the shell model to the equivalent beam model. From the dynamic characteristics of the beam model, it was found out that natural frequencies are proportional to the length of Reactor Core & Core Shroud and inversely proportional to the mass. From the comparison with the dynamic characteristics of a beam model and a lumped-mass model it was found out that the size of lumped-mass must be determined considering both the length and the mass of Reactor Core & Core Shroud.

• 한국주조공학회지
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• 제17권4호
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• pp.402-410
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• 1997

Developing a salt core for squeeze casting process, two different salt cores(pure salt core and mixed salt core) were fabricated and investigated. Pure salt core was composed of 100% NaCl and mixed salt core was made by mixtures of NaCl with MgO(1%), $Na_2B_4O_7$(2%), and talc(1%) as a binder or a strengthening agent. Salt cores were compacted to various theoretical density, heat treated, and then squeeze-cast with molten Al alloy(AC8A). The compression strength of salt cores were measured and the squeeze-cast products were examined for shape retention, infiltration of molten metal into the cores, and microstructures. The shape of salt core compacted at above 75% of the theoretical density was maintained stably. The higher theoretical density of salt cores gave higher compression strength, and the compression strength of mixed salt core was higher than that of pure salt core. Namely at 90% theoretical density, the compression strength of mixed salt core was $6.3 kg/mm^2$, compared to $4.6 kgmm^2$ for pure salt core. At a squeeze casting pressure of $1000 kg/cm^2$, molten Al alloy was infiltrated into pure salt core of under 85% of the theoretical density. At squeeze casting pressure of $1000 kg/cm^2$, only mixed salt core above 90% of the theoretical density were valid, but the shape of the core was altered in the case of pure salt core at 90% of theoretical density. A key factor for developing a salt core for squeeze casting process was estimated as the ultimate compressive strength of salt core.

• Nuclear Engineering and Technology
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• 제36권6호
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• pp.528-539
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• 2004

It is essential in commercial reactors that the safety limits imposed on the fuel pellets and fuel clad barriers, such as the linear power density (LPD) and the departure from nucleate boiling ratio (DNBR), are not violated during reactor operations. In order to accurately monitor the safety limits of current reactor states, a detailed three-dimensional (3D) core power distribution should be estimated from the in-core detector signals. In this paper, we propose a calculation methodology for detailed 3D core power distribution, using in-core detector signals and core monitoring constants such as the 3D Coupling Coefficients (3DCC), node power fraction, and pin-to-node factors. Also, the calculation method for several core safety parameters is introduced. The core monitoring constants for the real core state are promptly provided by the core design code and on-line MASTER (Multi-purpose Analyzer for Static and Transient Effects of Reactors), coupled with the core monitoring program. through the plant computer, core state variables, which include reactor thermal power, control rod bank position, boron concentration, inlet moderator temperature, and flow rate, are supplied as input data for MASTER. MASTER performs the core calculation based on the neutron balance equation and generates several core monitoring constants corresponding to the real core state in addition to the expected core power distribution. The accuracy of the developed method is verified through a comparison with the current CECOR method. Because in all the verification calculation cases the proposed method shows a more conservative value than the best estimated value and a less conservative one than the current CECOR and COLSS methods, it is also confirmed that this method secures a greater operating margin through the simulation of the YGN-3 Cycle-1 core from the viewpoint of the power peaking factor for the LPD and the pseudo hot pin axial power distribution for the DNBR calculation.

• BMB Reports
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• 제31권3호
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• pp.281-286
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• 1998

Hepatitis C virus (HCV) core proteins from two different isolates (HCV-1 and HCV-RH) were expressed in Spotioptera Jrugiperda (Sf9) insect cells. The RH core consisted of two major species of proteins (21 kDa and 19 kDa). On the other hand, the HCV-1 core was approximately 16 kDa in a SDS-PAGE gel. Both core proteins were phosphorylated in vivo on serine residues. Furthermore, the RH core but not HCV-1 core formed dimers, indicating that the protein conformation of the core in these two isolates is dfferent from one another. Immunofluorescence studies showed that the RH core was present in the cytoplasm, whereas the HCV-1 core was localized predominantly to the nucleus in recombinant baculovirus-infected insect cells. Since the major difference between the two isolates is the codon 9 of the core protein, a single amino acid substitution appears to play a major role in the protein conformation and these properties may reflect the different biological functions of core proteins in HCV-infected cells.

• 한국통신학회논문지
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• 제25권1A호
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• pp.90-95
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• 2000

Ordered Core Based Tree (OCBT) 프로토콜에서 core 스위치의 위치는 성능에 영향을 끼치는 가장 중요한 요소이다. 본 논문에서는 여러 level의 core 스위치를 어디에 둘 것인가에 대한 방법을 연구한다. 제안된 알고리즘은 전체 네트워크는 3개의 논리적 계층-Small, Medium, Large-으로 나누어, 네트워크의 각 노드(라우터)들은 자기 이와의 다른 노드들로부터 자신의 노드까지의 최단경로 비용의 합을 계산한다. S지역에서 최소의 비용을 가지는 노드를 core노드로 만들고, 같은 M지역에 속한 S지역의 core 노드들은 다른 core 노드들로부터의 최단 경로 합을 계산해서 그 값이 가장 작은 노드가 레벨이 하나 높은 core 노드가 된다. 그리고 M지역에서의 core노드에서 같은 방법으로 가장 높은 레벨을 가지는 core노드를 정한다. 제안한 방법을 네트워크에서 core 노드를 정하는 두 가지 일반적인 방법과 비교한다. 첫 번째 방법은 random 방법으로 같은 수의 core 노드를 random하게 선정하는 방법이다. 두 번째 방법은 center 방법으로 각각의 S지역에서 중심에 가까운 노드를 core 노드로 만들고, M지역이나 L 지역에서의 core는 하위 레벨 core 중에서 해당 熾だ\ulcorner중심에 가까운 core로 결정한다. 시뮬레이션을 통하여 제안한 방법이 mean tree cost와 join latency관점에서 비교된 다른 방법들 보다 우월한 성능을 가지는 것을 확인할 수 있었다.

• IEIE Transactions on Smart Processing and Computing
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• 제4권2호
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• pp.83-88
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• 2015

Core-A is 32-bit synthesizable processor core with a unique instruction set architecture (ISA). In this paper, the Core-A ISA is introduced with discussion of useful features and the development environment, including the software tool chain and hardware on-chip debugger. Core-A is described using Verilog-HDL and can be customized for a given application and synthesized for an application-specific integrated circuit or field-programmable gate array target. Also, the GNU Compiler Collection has been ported to support Core-A, and various predesigned platforms are well equipped with the established design flow to speed up the hardware/software co-design for a Core-A-based system.

• 접착 및 계면
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• 제11권3호
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• pp.112-119
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• 2010

PMMA와 PBA core 제조 시 개시제는 APS를, 유화제 SDBS의 농도를 0.01에서 0.03 wt% 일 때 전환율이 95.8과 92.3%로 가장 우수하였으며, core-shell 복합입자의 제조 시에는 SDBS의 농도 0.02 wt% 일 때 PMMA/PBA core-shell 복합입자는 전환율이 90.0%, PBA/PMMA core-shell 복합입자는 89.0%가 되었다. FT-IR 분석과 GPC에 의한 평균분자량 측정을 통해 core와 shell 단량체들이 중합되어 있음을 확인하고, 복합입자의 형태는 상온에서의 필름형성정도와 TEM 분석으로 확인하였다. DSC에 의해 유리전이온도를 측정함으로써 일반 공중합체와는 달리 2개의 유리전이온도가 존재하여 core-shell 복합입자가 형성되었음을 알 수 있고, 각각의 core-shell 복합입자의 인장강도와 신율의 측정을 통해 고기능성 접착바인더로서의 사용가능성을 확인하였다.

• 폴리머
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• 제32권5호
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• pp.470-477
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• 2008

아크릴계 단량체인 MMA, St, EA, BA 및 관능성 단량체인 2-HEMA 단량체를 수용성 개시제인 APS와 음이온 유화제인 SDBS를 사용하여 한 입자 내에 서로 다른 물성을 나타내는 core shell 구조의 바인더를 중합 후 부직포에 처리하여 기계적 물성을 평가하였다. Core shell 바인더 중합시 단량체 조성에 관계없이 개시제는 1.0 wt%/단량체의 농도를 가지는 APS와 0.04 wt%/단량체의 유화제를 사용했을 때 가장 높은 전환율을 나타내었고, core shell 바인더의 유리전이온도는 공중합체의 단일 전위 곡선에 비하여 core shell 바인더는 2개 이상의 전이곡선을 얻었다. 부직포에 core shell 바인더를 처리 후 인장강도 및 신장율 측정에서 관능성 단량체를 사용한 PSt/PMMA/2-HEMA core shell 바인더가 $10.75\;kg_f$/2.5 cm로 가장 높은 값을 나타내었고, 신장율 측정에는 PEA/PBA core shell 바인더가 120.00%로 가장 높은 값을 나타내었다. 결론적으로 core shell 바인더를 사용하여 부직포의 기계적 물성을 조절할 수 있었다.

• 생명과학회지
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• 제32권2호
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• pp.94-100
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• 2022

B형간염바이러스(HBV)의 만성 감염은 간경화와 간세포암 발생 빈도를 현저히 높인다. HBV 감염의 임상적 결과는 숙주 유전적 요인과 바이러스의 유전자 변이, 그리고 환경적 요인 등에 결정된다. HBV 복제를 위한 HBV의 pre-genomic RNA 전사는 바이러스의 core promoter 활성화에 의해 조절된다. Core promoter 돌연변이는 급성간 질환과 간세포암 발생에 연관되어 있다. 본 연구팀은 미얀마의 HBV 감염 환자들로부터 바이러스 유전자를 획득하여 core promoter 부위의 유전자 변이들을 파악하였다. Core promoter의 상대적 유전자 활성 차이를 분석하기 위해서 core promoter를 luciferase reporter에 재조합한 시스템을 제작하였다. 분석한 core promoter의 유전자 변이들 중에서 C1731T와 G1806A 돌연변이가 HBV core promoter의 전사 활성화를 증가에 관여하였다. 돌연변이 부위를 중심으로 전사 인자들의 가능한 결합 부위 변화를 컴퓨터 프로그램 분석을 통해 조사한 결과, C/EBPβ와 XBP1 반응 부위가 새롭게 생성되었음을 도출하였다. C/EBPβ의 세포 내 발현은 C1713T 돌연변이를 가진 core promoter의 전사 활성을 증가시켰으며, XBP1 발현은 G1806A 돌연변이를 함유한 M95 promoter를 활성을 증가시켰다. HBV 감염의 치료는 약제 내성과 백신 회피 돌연변이 발생으로 문제점을 가지고 있는 상황에서, 이 연구 결과는 HBV core promoter 돌연변이의 분자생물학적 그리고 임상학적 중요성을 제공한다.