• 한국시뮬레이션학회논문지
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• 제27권1호
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• pp.15-24
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• 2018

HLA(High Level Architecture)는 시뮬레이션의 재사용성 증진과 상호운용성 확보를 목표로 하는 국제기술표준이다. 전세계적으로 HLA 기반 페더레이트 간의 연동을 통한 페더레이션 구축이 다양한 분야에서 적용되고 있으며, 국내 군사 분야에서는 KR/UFG 한미 연합연습 등에서 활용되고 있다. 현재 미 국방성에서는 페더레이트의 HLA 준수여부를 사전에 확인하는 HLA 적합성 인증시험이 강조되고 있다. 그러나 미국의 인증시험은 인증도구의 제한사항으로 인해 페더레이션 저장/복구 서비스 등 일부 HLA/RTI 서비스들에 대한 기능검사는 불가능하며 페더레이트 간의 교환데이터에 대한 검사 또한 배제되어 있다. 본 논문은 이러한 문제를 해결하기 위해 국내 실정에 맞는 한국형 HLA 적합성 인증시험 체계를 제안한다. 이를 통해 효과적인 인증시험 수행이 가능하며 각 페더레이트들 간의 상호운용성을 향상시킬 수 있을 것으로 기대한다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 추계학술대회논문집
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• pp.163-167
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• 2003

The large deformation at cryogenic temperature would be one of the effective methods to produce large bulk UFG materials. The effects of annealing temperature 150∼300$^{\circ}C$, on microstructure and mechanical properties of the sheets received 85% reduction at cryogenic temperature were investigated. In comparison with those at room temperature. Annealing of 5083 Al alloy deformed 85%, at 200$^{\circ}C$ for an hour, results in the considerable increase of tensile elongation without the great loss of strength and the occurrence of equiaxed grains less than 300nm in diameter.

• 동력기계공학회지
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• 제15권1호
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• pp.45-50
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• 2011

The effect of Mn and Ti contents in filler wire on the microstructure and mechanical property of weld metal has been investigated after hybrid welding with ultra fine grained (UFG) steel. The microstructure and distribution of alloy compositions at the top region of weld zone were quite different with those at the bottom region after hybrid welding. The bottom region of weld zone contained higher Mn and Ti contents, and consequently the hardness of bottom region was higher than that of top region. With the increase of Mn and Ti contents in filler wire, the volume percent of acicular ferrite in weld metal decreased, and the weld zone showed higher hardness and better impact property.

• 월간피드저널
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• 제3권7호통권23호
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• pp.65-70
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• 2005

어분의 미지성장인자(UGF)중 하나는 오메가($\omega$)-3 지방산 - 동물성 단백질의 왕자라고 할 어분은 전 세계적으로 양어사료는 물론 양계사료 및 이유자돈 사료로 널리 이용되어 왔다. 특히 어분의 미지성장인자(UFG ;Unknown Growth factor)인 오메가($\omega$)-3 지방산은 면역체세포의 활력도 증진시키는 작용도 하고 있는 것으로 밝혀졌다. 하지만 1970년대 초, 미국의 어분생산량이 급격히 감소하면서부터 가축사료의 단백질 공급원으로서 어분이 차지하던 자리는 대두박 등의 식물성 박류에게 넘겨줄 수 밖에 없었다. 그럼에도 불구하고, 단미사료의 80($\%$를 수입에 의존하여, `보세가공 축산`이라는 부정할 수 없는 꼬리표까지 달고 있는 우리나라가 어분의 생산량만큼은 충분하다고하니 반가운 일이 아닐 수 없다. 어분의 사료영양학적 가치를 제대로 파악하여 우리나라 부존자원의 활용을 높이는 것은 국가적으로도 이익이 아닐수 없을 것이다. 본고에선 그러한 어분의 영양학적 특징과 미지성장인자(未知成長因子)의 역할 중 오메가($\omega$)-3 지방산 및 단백질 공급원으로써의 어분을 양계사료 및 이유자돈 사료에 이용함으로써 얻어지는 이익에 대해 논하고자 한다.

• 대한수학회보
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• 제53권2호
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• pp.531-540
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• 2016

In this work, we introduce the complete Riemannian manifold $\mathbb{F}_3$ which is a three-dimensional real vector space endowed with a conformally flat metric that is a solution of the Einstein equation. We obtain a second order nonlinear ordinary differential equation that characterizes the helicoidal minimal surfaces in $\mathbb{F}_3$. We show that the helicoid is a complete minimal surface in $\mathbb{F}_3$. Moreover we obtain a local solution of this differential equation which is a two-parameter family of functions ${\lambda}_h,K_2$ explicitly given by an integral and defined on an open interval. Consequently, we show that the helicoidal motion applied on the curve defined from ${\lambda}_h,K_2$ gives a two-parameter family of helicoidal minimal surfaces in $\mathbb{F}_3$.

• 소성∙가공
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• 제27권4호
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• pp.222-226
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• 2018

Severe plastic deformation (SPD) is a promising method for drastically enhancing the mechanical properties of the materials by grain refinement of metallic materials. However, inhomogeneous deformation during the SPD process results in the inhomogeneous microstructure of the SPD-processed material. We manufactured cylindrical copper specimens of 42 mm in diameter with ultrafine grains (UFG) using an equal channel angular pressing (ECAP) to figure out the relationship between homogeneous microstructure and the number of the processing passes. Two specimens, which are ECAP-processed 4 times (4pass) and 6 times (6pass) each with Route Bc, are prepared for comparison of mechanical properties and microstructure. The results show that the mechanical properties of the two specimens (4pass and 6pass) are similar. Moreover, both the specimens show highly enhanced mechanical properties. The 4pass specimen, however, shows inhomogeneity in hardness distribution, while the 6pass specimen shows a homogeneous distribution. Microstructure analysis reveals that the 4pass specimen has an inhomogeneous microstructure with incompletely refined grain structure. This inhomogeneity of the 4pass specimen could be explained by the circumferential rotation during ECAP process.

• 대한금속재료학회지
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• 제50권1호
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• pp.86-91
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• 2012

Ti-6Al-4V extra low interstitial (ELI) alloy has been widely used as an orthopedic implant material because of its excellent biocompatibility, corrosion resistance and mechanical properties. However, V-free titanium alloys such as Ti-6%Al-7%Nb and Ti-5%Al-2.5%Fe have recently been developed because of the toxicity of V. Hydroxyapatite (HA) is used as a coating material on Ti or Ti biomaterials due to its good biocompatibility. However, HA coated on Ti alloy causes a problem for tissue by peeling off during usage. Therefore, such peeling off during long time usage can be suppressed by adding HA in Ti or Ti alloy composites. The aim of this study was to manufacture an ultra fine grained (UFG) Ti-Nb-HA bulk alloy, which is usually difficult to fabricate using melting and casting technology, by rapid sintering process using high energy mechanical milled (HEMM) powder.

• 대한금속재료학회지
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• 제50권6호
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• pp.469-475
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• 2012

A high-energy mechanical milling (HEMM) process was introduced to improve sinter-ability, and rapid sintering of spark plasma sintering (SPS) under pressure was used to make ultra fine grain (UFG) of Ti-Nb-Mo-CPP composites, which have bio-attractive elements, for increasing mechanical properties. Ti-Nb-Mo-CPP composites were successfully fabricated by SPS at $1000^{\circ}C$ within 5 minutes under 70 MPa using HEMMed powders. The Vickers hardness of the composites increased with increased milling time and addition of CPP contents. Biocompatibility and corrosion resistance of the Ti-Nb-Mo alloys were improved by addition of CPP, and the Ti-35%Nb-10%Mo-10%CPP alloy had better biocompatibility and corrosion resistance than the Ti-6Al-4V ELI alloy.

• Strategy21
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• 통권41호
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• pp.294-332
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• 2017

The aim of this study is to find ways to apply the strategic communications to the Republic of Korea Navy. It may be a little bit late for the ROK Navy to accommodate the SC in these days because the adoption and implementation of the SC by the Combined Forces Command has already been begun. It was in 2007 when the SC was in place in the CFC. ROK's Ministry of National Defense and Joint Chiefs of Staff have also mulled over the SC and begun to apply it in part in the annual exercises such as Key Resolve command post drills and Foal Eagle field training exercise, etc. For the ROK Navy, in addition to those exercises, it is faced with further areas like North Korean maritime provocations and other maritime incidents where its version of SC is needed. As noted, the SC is not intended to deter or defend directly those provocations and incidents, but aims to create conditions favorable to the achievement of the navy's strategic objectives. The ROK Navy has to establish a SC planning center and implementing organizations within the Headquarters to be consistent with its above organizations such as MND, JCS, and CFC that have already applied the SC in part or in entirety. SC center and other related organizations need to be under the control of VCNO and the center needs to be located and administered by the policy division in N-5 at the HQs. The vision of the navy's SC is the winning without combats and the least damages in time of war. In other for the navy to reach the vision, the strategies to be executed are early establishment of SC implementing organizations, forming consensus over the need for the SC within the navy, strengthening core competencies to apply the SC, acquiring the SC experts and making doctrines on the SC. The SC, in addition, in the navy has to be planned and implemented in not only peace time and crisis time but also war time.

• 한국재료학회지
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• 제22권11호
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• pp.615-619
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• 2012

Recently, ultrafine grained (ufg, typically 100 > d > 500 nm) Ti-Fe eutectic materials have been highlighted due to their extraordinarily high strength and good abrasion resistance compared to conventional coarse grained (cg, d > $1{\mu}m$) materials. However, these materials exhibit limited plastic strain and toughness during room temperature deformation due to highly localized shear strain. Several approaches have been extensively studied to overcome such drawbacks, such as the addition of minor elements (Sn, Nb, Co, etc.). In this paper, we have investigated the influence of the addition of Gd and Y contents (0.3-1.0 at.%) into the binary Ti-Fe eutectic alloy. Gd and Y are chosen due to their immiscibility with Ti. Microstructural investigation reveals that the Gd phase forms in the eutectic matrix and the Gd phase size increases with increasing Gd content. The improvement of the mechanical properties is possibly correlated to the precipitation hardening. On the other hand, in the case of Ti-Fe-Y alloys, with increasing Y contents, primary phases form and lamellar spacing increases compared to the case of the eutectic alloy. Investigation of the mechanical properties reveals that the plasticity of the Ti-Fe-Y alloys is gradually improved, without a reduction of strength. These results suggest that the enhancement of the mechanical properties is closely related to the formation of the primary phase.