• 한국방재학회 논문집
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• 제4권3호
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• pp.73-81
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• 2004

본 연구에서는 염해에 대한 내구성 저하 요인을 국내외 자료에 의해 요인별 분석, 고찰하고 Fick의 확산 방정식을 적용하여 설계기준강도와 물-시멘트비에 따른 염화물의 확산계수와 내구년한에 의한 환경조건별 소요피복두께를 산출하여 각 변수들의 변화에 따른 영향을 고찰하였다. 물-시멘트비가 감소하고 설계강도가 증가되면 염화이온의 침투속도가 낮아져 소요피복두께를 줄이는 것으로 나타났다. 특히 비말대 환경조건에서 고강도 콘크리트에 고로슬래그 시멘트를 사용할 경우 염화이온의 확산을 막는데 더욱 효과적이였다. 결과적으로 고내구성을 필요로 하는 해양콘크리트 구조물의 경우 최소피복두께 기준인 8cm보다 환경조건에 따라 $3{\sim}8cm$의 피복두께가 증가되어야 1등급 내구년한을 만족시키는 것으로 나타났다.

• 한국재료학회지
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• 제31권8호
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• pp.439-444
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• 2021

The oxidation resistance of the diffusion aluminide bond coat (BC) is compromised largely by interdiffusion (ID) effects on coated turbine blades of aeroengines. The present study is designed to understand the influence of ID on βNiAl coatings or BC. In this regard, nickel substrate and CMSX-4 superalloy are deposited. In total, four sets of BCs are developed, i.e. pure βNiAl (on Ni substrate), simple βNiAl (on CMSX-4 substrate), Zr-βNiAl (on CMSX-4 substrate) and Pt-βNiAl (on CMSX-4 substrate). The main aim of this study is to understand the interdiffusion of Al, Zr and Pt during preparation and oxidation. In addition, the beneficial effects of both Zr and platinum are assessed. Pure βNiAl and simple βNiAl show Ni-out-diffusion, whereas for platinum inward diffusion to the substrate is noticed under vacuum treatment. Interestingly, Zr-βNiAl shows the least ID in all BCs and exhibit stability under both vacuum and oxidation treatments. However, its spallation resistance is slightly lower than that of Pt-βNiAl BC. All BCs show similar oxide growth trends, except for Zr-βNiAl, which exhibits two-stage oxidations, i.e. transient and steady-state. Moreover, it is suggested that the localized spallation in all BCs is caused by βNiAl - γ'-Ni₃Al transformation.

• 한국재료학회지
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• 제14권2호
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• pp.126-132
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• 2004

The high strength steel sheets has been widely used as the automobile parts to reduce the weight of a vehicle. The aim of this research is to develop the TRIP aided high strength low carbon steels using reverse transformation process. The 0.15C-4Mn and 0.15C-6.5Mn steel sheets were reversely transformed by slow heating to intercritical temperature region and air cooling to room temperature. The stability of retained austenite depends on the enrichment of carbon and manganese by diffusion during the reverse transformation. The amount of retained austenite formed after reversely transformed at $645^{\circ}C$ for 12 hrs. was about 46vol.% in hot rolled 0.lC-6.5Mn steel. The change in volume fraction of retained austenite with a holding temperature was consistent with the changes in elongation and the strength-ductility combination. The tendency of tensile strength to increase with increasing the holding temperature was due to the decrease of retained austenite after cooling from the higher temperature of $670 ^{\circ}C$. The maximum strength-ductility combination was about 4,250 kg/$\textrm{mm}^2$ㆍ% when the hot rolled 0.lC-6.5Mn steel was reversely transformed at $645^{\circ}C$ for 12 hrs.

• International Journal of Computer Science & Network Security
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• 제22권1호
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• pp.340-346
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• 2022

The article examines the formation of the scientific paradigm of transformation of the potential-forming space of the regional economy under the influence of intellectual and innovative determinants. Based on the study of different scientific views on the nature and properties of potential-forming space through the study of approaches to understanding the concept of "space" clarified the complexity and multifaceted nature of the phenomenon and found that its characteristics are relevant to the industrial development model. It is revealed that the leading modern trends related to the spread of globalization and regionalization, rapid development of information and communication technologies, diffusion of innovations accompany the transition from industrial to post-industrial development and its development, which leads to new development: changes production, nature and relations between business entities, etc. It is proved that under such conditions, the region as a key element of the economic system, acquires a leading role in achieving sustainable and balanced development. These processes significantly affect the potential-forming space of the regional economy under the influence of intellectual and innovative determinants, leading to the need for its transformation and change in accordance with modern realities, which is reflected in thorough research on the formation of scientific paradigm based on the formation of its theoretical foundations and methodological basis. This study reveals the essence, role, functions, structure, process of formation of the scientific paradigm of transformation of the potential-forming space of the regional economy under the influence of intellectual and innovative determinants. It is proved that the formation of the modern scientific paradigm of transformation of the potential-forming space of the regional economy under the influence of intellectual and innovative determinants occurs in the context of building a post-industrial model of development, accompanied by consideration of the region as a spatial object territories from the physical plane to the spatial environment in which the development of human capital, innovation and self-development of the region. Taking into account the above, the article outlines the prerequisites and factors of formation of the scientific paradigm of transformation of the potential-forming space of the regional economy under the influence of intellectual and innovative determinants.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1172-1177
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• 2004

The evolution of incipient soot particles has been examined by high resolution electron microscopy (HRTEM) and elemental analyzer in ethylene-air inverse diffusion flames. Laser Induced Incandescence(LII) and laser scattering methods were introduced for examining the change of soot volume fraction and morphological properties in combustion generated soot qualitatively. Soot particles, collected by thermophoretic sampling were analyzed by using HRTEM to examine the nano structure of precursor particles. HRTEM micrographs apparently reveal a transformation of condensed phase of semitransparent tar-like material into precursor particles with relatively distinct boundary and crystalline which looks like regular layer structures. During this evolution histories C/H analysis was also performed to estimate the chemical evolution of precursor particles. The changes of C/H ratio of soot particles with respect to residence time can be divided into two parts: one is a very slowly increasing regime where tar-like materials are transformed into precursor particles (inception process) the other is an increasing region with constant rate where surface growth affects the increase of C/H ratio dominantly (surface growth region). These results provide a clear picture of a transition to mature soot from precursor materials.

• 한국항행학회논문지
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• 제11권1호
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• pp.112-117
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• 2007

현대 사회는 인터넷의 급속한 보급과 발전으로 사회활동 전반에 걸친 변화를 주도하고 있으며, 새로운 형태의 상거래인 인터넷을 이용한 전자상거래(Electronic Commerce)가 확산 발전되고 있다. 본 논문에서는 공용 키 (PKI)에 기초를 두는 네트워크형 전자지불 프로토콜을 제안하고자 한다. 제안된 프로토콜은 컨텐츠 거래를 위해 개발된 NetBill 시스템의 익명성을 보장하지 못했던 단점을 보완하였다. 또한 온라인 상에서 제공된 디지털 콘텐츠에 대해 인증번호를 부여함으로써 무단 복제를 방지하고 최대한 안전성이 확보되도록 하였다.

• 멤브레인
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• 제21권3호
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• pp.229-235
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• 2011

본 연구에서는 메조기공 티타니아/알루미나 막을 솔-젤법을 이용하여 제조하였다. 티타니아/알루미나 막의 기공구조 및 결정상은 하소 온도에 따라 조절될 수 있었다. 티타니아에 알루미나를 첨가하는 것은 티타니아 결정상이 아나타제상에서 루타일상으로 상변화 되는 것을 지연시켜 기공구조의 열적 안정화를 가져왔다. 5번 딥코팅하여 제조된 막의 두께는 $10.3{\mu}m$였으며, 평균 기공크기는 5 nm이었다. 기체 투과 실험 결과는 수소와 질소의 permeance는 각각 $17.1{\tiems}10^{-7}mol/m^2{\cdot}s{\cdot}Pa$ 및 $4.7{\tiems}10^{-7}mol/m^2{\cdot}s{\cdot}Pa$이었다. 이 결과는 Knudsen 확산에 의해 설명될 수 있었다.

• 한국연소학회지
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• 제9권2호
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• pp.38-44
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• 2004

The evolution of incipient soot particles has been examined by high resolution electron microscopy (HRTEM) and elemental analyzer in ethylene-air inverse diffusion flames. Laser Induced Incandescence(LII) and laser scattering methods were introduced for examining the soot volume fraction and morphological properties in combustion generated soot qualitatively. Soot particles, collected by thermophoretic sampling, were analyzed by using HRTEM to examine the nano structure of precursor particles. HRTEM micrographs apparently reveal a transformation of condensed phase of semitransparent tar-like material into precursor particles with relatively distinct boundary and crystalline which looks like regular layer structures. During this evolution histories, C/H analysis was also performed to estimate the chemical evolution of precursor particles. The changes of C/H ratio of soot particles with respect to residence time can be divided into two parts: one is a very slowly increasing regime where tar-like materials are transformed into precursor particles (inception process) the other is an increasing region with constant rate where surface growth affects the increase of C/H ratio dominantly (surface growth process). These results provide a clear picture of a transition to mature soot from precursor materials.

• Investigative Magnetic Resonance Imaging
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• 제22권2호
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• pp.131-134
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• 2018

Susceptibility-weighted imaging (SWI) is well known for detecting the presence of hemorrhagic transformation, microbleeds and the susceptibility of vessel signs in acute ischemic stroke. But in some cases, it can provide the tissue perfusion state as well. We describe a case of a patient with hyperacute ischemic infarction that had a slightly hypodense, patchy lesion at the left thalamus on the initial SWI, with a left proximal posterior cerebral artery occlusion on a magnetic resonance (MR) angiography and delayed time-to-peak on an MR perfusion performed two hours after symptom onset. No obvious abnormal signals at any intensity were found on the initial diffusion-weighted imaging (DWI). On a follow-up MR image (MRI), an acute ischemic infarction was seen on DWI, which is the same location as the lesion on SWI. The hypointensity on the initial SWI reflects the susceptibility artifact caused by an increased deoxyhemoglobin in the affected tissue and vessels, which reflects the hypoperfusion state due to decreasing arterial flow. It precedes the signal change on DWI that reflects a cytotoxic edema. This case highlights that, in some hyperacute stages of ischemic stroke, hypointensity on an SWI may be a finding before the hyperintensity is seen on a DWI.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 제3회 압연심포지엄 논문집 압연기술의 미래개척 (Exploitation of Future Rolling Technologies)
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• pp.356-365
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• 1999

The present study is aimed at developing the TRIP(transformation induced plasticity) aided high strength low carbon steel using reversion process. An excellent combination of elongation over 40% and tensile strength abut 100kgf/$\textrm{mm}^2$ achieved in processing of 0.15C-0.5 Si-6Mn steel by slow heating to intercritial temperature region and accelerated cooling into room temperature. This good combination is caused by TRIP phenomena of retained austenite in steels during deformation. The stability of retained austenite is very important for the good ductility and it depends on the diffusion of carbon and manganeses during heat treatment. The accelerated cooling after holding at annealing temperature retards the formation of pearlite and provides the carbon enrichment in retained austenite in steel, resulting in the increase in elongation of the cold-rolled TRIP steel. On the other hand, heat treating the steel at 600$^{\circ}C$ for 5 hour before cold rolling increases elongation but reduces the amount of retained austenite after reversion processing. It is accounted that the heat treating is effective for the increase in the stability of retained austenite.