Effect of Inhomogeneous Nucleation of Hydride at α/β Phase Boundary on Microstructure Evolution of Zr–2.5 wt%Nb Pressure Tube

Sung‑Soo Kim,Sangyeob Lim,Dong‑Hyun Ahn,Gyeong‑Geun Lee,Kunok Chang 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.4

We analyzed the microstructural characteristics such as number density and length and width of hydrides in Zr–2.5 wt%Nbpressure tube. The hydrogen was charged cathodically and the hydride-contained sample was evaluated using the advancedanalysis methodologies. We performed a diff erential scanning calorimetry analysis to more quantitatively understand thethermodynamics of the hydride formation/growth process. We characterized the micrograph of hydride-contained Zr samplesto estimate the microstructural characteristics of the matrix and hydrides. We investigated eff ects of hydrogen concentrationand microstructure of matrix on determining microstructural measures of the hydrides. Particularly, we found that β phasein the matrix becomes isolated during the heat treatment same or above 475 °C and this change increases the inhomogeneousnucleation sites signifi cantly. We claim that the microstructure change of this matrix phase greatly increases the numberdensity of hydride.

정부운영 방식으로서의 정부3.0 재조명: 문재인 정부의 정부3.0 정책 계승을 위한 제언

임성근 ( Sung Geun Lim ),이건 ( Geon Lee ) 중앙대학교 국가정책연구소 2017 국가정책연구 Vol.31 No.3

본 연구는 박근혜 정부 4년 동안 국가운영의 한 패러다임으로서 위상을 가졌던 정부3.0 정책의 추진 현황을 회고하며, 그 핵심적 내용을 정리하고, 일반국민, 공무원, 전문가들이 정부3.0을 어느 정도로 중요하게 인식하고 필요성을 체감하고 있는지를 탐색하였다. 본 연구에서 제시한 조사결과에 의하면, 일반국민, 공무원, 전문가 모두 정부3.0의 필요성을 절감하고 있으며 정부3.0의 제 목표 및 핵심과제가 중요하다는데 인식을 같이하고 있다. 그러나 정부3.0 핵심과제에 대한 만족도 및 주관적인 추진성과에 대한 평가는 중요성에 비하여 낮게 인식하고 있다. 이는 정부3.0의 정착은 아직 미흡하고 더욱 발전시킬 여지가 있음을 말해준다. 좋은 제도가 정착되기도 전에 정권의 변동으로 폐기되는 것은 그동안 투입되었던 매몰비용 및 국민들이 누리는 편익을 고려할 때 비효율적이라 할 수 있다. 문재인 정부는 전문가들과의 공론화 과정을 거쳐 미완의 정부3.0 정책을 승계하여 보다 높은 수준으로 발전ㆍ완성시킴으로써 국민에게 유익한 정책은 정권이 교체되더라도 지속될 수 있음을 보여주는 첫 모범 사례가 되기를 기대한다. This study recalls the implementation progress of the Government 3.0 policy, which has been the paradigm for government administration for four years during the Park Geun-hye Administration, and summarizes its core contents. It also explores how the public, public officials and experts assessed the significance of Government 3.0, and whether they felt its necessity. According to the results of this study, the general public, public officials and experts all felt the need for Government 3.0 and shared an understanding that the goals and core tasks of Government 3.0 are still highly relevant. However, their overall assessment of the satisfaction level and subjective performance of the core projects of Government 3.0 was relatively lower than their perceived importance of the initiative, suggesting that Government 3.0 has yet to take root firmly in place and that there still is a room for further development. It would be a waste of valuable resource to junk the policy initiative even before the good system has been firmly established, considering the immense sunk cost and the benefits enjoyed by the people. We suggest that the Moon Jae-in Administration would promote and complete the unfinished missions of the Government 3.0 policy initiative through a public deliberation with related experts, thereby establishing itself as the first best case to demonstrate that beneficial policies for the people can be maintained even after the regime has been replaced.

종 분포 모형을 이용한 구상나무림의 지속 및 쇠퇴에 관한 연구 - 전라남도 광양시 백운산을 중심으로 -

조선희 ( Seon Hee Cho ),박종영 ( Jong Young Park ),박정호 ( Jeong Ho Park ),이양근 ( Yang Geun Lee ),문이만 ( Lee Man Mun ),강상호 ( Sang Ho Kang ),김광현 ( Gwang Hyun Kim ),윤종국 ( Jong Guk Yun ) 한국산림과학회 2015 한국산림과학회지 Vol.104 No.3

The present study investigated the habitats of Korean fir trees (Abies koreana E. H. Wilson) on Mt. Baekwun (Baekwun-san), determined the current distribution, quantified the contribution of biological and nonbiological environmental factors affecting the distribution, derived actual and potential habitats, presented a plan for the establishment of protected areas, applied RCP 8.5 climate change scenario to analyze the effects of climate change on the future distribution of Korean fir trees, and predicted future potential habitats. According to the results of the study, 3,325 Korean fir trees (DBH >= 2.5 cm) inhabited Mt. Baekwun, and their distribution area was approximately 150 ha. Populations of Korean fir trees were confirmed to exist at an altitude of 900 m above sea level and were distributed up to 1,200 m. Based on potential distribution, areas appropriate for habitation by Korean fir trees were analyzed to be 450 ha, three times the current distribution area, with a focus on Sang Peak (Sang-bong), Eokbul Peak (Eokbul-bong), Ddari Peak (Ddari-bong), and Dosol Peak (Dosol-bong). The forest stands near Sang Peak, the main peak, were evaluated as those with the most appropriate potential for the habitation of Korean fir trees, and populations of the trees tended to prefer the northern slope rather than the southern slope. When climate change scenario RCP 8.5 was applied and future potential distribution was analyzed, the habitats were expected to decrease in area to 20 ha by 2050, with a focus on Sang Peak, and areas appropriate for habitation were predicted not to exist by 2080. Judging from such results, as global warming accelerates, the habitats of Korean fir trees are clearly expected to move from lowlands to highlands.

Improvement of the water resistance of atactic poly(vinyl alcohol) nanowebs by a heat treatment

Lee, Sung Jun,Lee, Se Geun,Kim, Hoyoung,Lyoo, Won Seok Wiley Subscription Services, Inc., A Wiley Company 2007 Journal of applied polymer science Vol.106 No.5

<P><B>Abstract</B></P><P>Nanoscale materials can be rationally designed to exhibit significantly changed physical, chemical, and biological properties because of the extremely small dimensions. Therefore, atactic poly(vinyl alcohol) (a‐PVA) nanowebs by an electrospinning technique have very high water solubility because of their nanoscale in comparison with microscale materials such as fibers and films. In this study, a‐PVA nanowebs were prepared via electrospinning under suitable conditions to form PVA webs with uniform nanofibers (fiber average diameter = 200 ± 50 nm), not a bead or bead‐and‐string morphology. Furthermore, to improve the water resistance of the water‐soluble a‐PVA nanowebs, the PVA nanowebs were heat‐treated at various heat‐treatment temperatures. The melting temperature of the heat‐treated PVA nanowebs shifted toward a lower temperature with an increase in the heat‐treatment temperature, and this indicated that micronetwork domains formed. Moreover, with the exception of a PVA nanoweb treated at an excessive heat‐treatment temperature, the heat‐treated PVA nanowebs showed higher crystalline and mechanical properties than a pure PVA nanoweb. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007</P>

Choroidal Thickness Variation According to Refractive Error Measured by Spectral Domain-optical Coherence Tomography in Korean Children

Geun Young Lee,Sung Yu,Hyun Gu Kang,Jin Seon Kim,Kyoo Won Lee,Jung-Ho Lee 대한안과학회 2017 Korean Journal of Ophthalmology Vol.31 No.2

Purpose: To assess choroidal thickness (CT) variation according to refractive errors using enhanced-depth imaging optical coherence tomography. Methods: Eighty-nine eyes (in 89 children) <±6 diopter were categorized into three groups: hyperopia, emmetropia, and myopia, according to refractive error, and underwent choroidal scans using enhanced-depth imaging-optical coherence tomography. CT was measured at the fovea and at 1 mm and 3 mm nasal (N1 and N3), temporal (T1 and T3), superior (S1 and S3), and inferior (I1 and I3) from the fovea. Results: Mean foveal CTs were 346.86 μm, 301.97 μm, and 267.46 μm in the hyperopia, emmetropia, and myopia groups, respectively (p < 0.05). CTs at N3 and T3 were 214.59 μm and 318.68 μm, 163.92 μm and 320.79 μm, and 153.93 μm and 295.61 μm in the hyperopia, emmetropia, and myopia groups, respectively (p < 0.05). All CTs in the hyperopia group were thicker than those of other groups (p < 0.05). Fovea was thickest and was significantly thicker than at N3 and I3 in hyperopia (p < 0.05). T3 thickness in the emmetropia and myopia groups was greater than thickness at other areas, particularly the nasal and inferior choroids (p < 0.05). CT was positively correlated with spherical equivalent (p = 0.029). Conclusions: In Korean children, CTs were greater in the hyperopia group than in the emmetropia and myopia groups. The temporal choroid was thicker than the nasal choroid, regardless of the refractive error. The thickest location in the hyperopia group was the fovea; however, the temporal choroid was thickest in the emmetropia and myopia groups.

The origin of enhanced L1₀ chemical ordering in Ag-doped FePt nanoparticles

Sung, Yun-Mo,Lee, Myung-Ki,Kim, Ki-Eun,Kim, Tae Geun Elsevier 2007 Chemical physics letters Vol.443 No.4

<P><B>Graphical abstract</B></P><P>Ag-doped FePt nanoparticles show enhanced A1-to-L1<SUB>0</SUB> chemical ordering due to the lowered activation energy, originating from the increased vacancy concentration.</P><ce:figure></ce:figure> <P><B>Abstract</B></P><P>FePt and Ag-doped FePt nanoparticles were synthesized by the thermolysis and polyol reductions. The A1-to-L1<SUB>0</SUB> transformation of the nanoparticles was investigated by differential scanning calorimetry (DSC) at different scanning rates, and the DSC endothermic peak shifts were monitored and used for the Kissinger analyses. The activation energy for the phase transformation was determined to be ∼251 and ∼219kJ/mol for the pure and doped FePt nanoparticles, respectively. The decrease in the activation energy is the evidence of increased number of vacancies, which turned out to be the origin for the reduced L1<SUB>0</SUB> chemical ordering temperature in doped FePt.</P>

Fully reconfigurable photonic microwave transversal filter based on digital micromirror device and continuous-wave, incoherent supercontinuum source

Lee, Ju Han,Chang, You Min,Han, Young-Geun,Lee, Sang Bae,Chung, Hae Yang The Optical Society 2007 Applied Optics Vol.46 No.22

<P>The combined use of a programmable, digital micromirror device (DMD) and an ultrabroadband, cw, incoherent supercontinuum (SC) source is experimentally demonstrated to fully explore various aspects on the reconfiguration of a microwave filter transfer function by creating a range of multiwavelength optical filter shapes. Owing to both the unique characteristic of the DMD that an arbitrary optical filter shape can be readily produced and the ultrabroad bandwidth of the cw SC source that is 3 times larger than that of Er-amplified spontaneous emission, a multiwavelength optical beam pattern can be generated with a large number of wavelength filter taps apodized by an arbitrary amplitude window. Therefore various types of high-quality microwave filter can be readily achieved through the spectrum slicing-based photonic microwave transversal filter scheme. The experimental demonstration is performed in three aspects: the tuning of a filter resonance bandwidth at a fixed resonance frequency, filter resonance frequency tuning at a fixed resonance frequency, and flexible microwave filter shape reconstruction.</P>

Three Dimensional Analysis of Thermal Stress and Prediction of Failure of Polytypoidally Joined SI₃N₄-AL₂O₃ Functionally Graded Material (FGM)

Lee, Caroline S.,Kim, Sung-Geun,Ahn, Sung-Hoon,DeJonghe, Lutgard C.,Thomas, Gareth THE JAPAN INSTITUTE OF METALS 2007 MATERIALS TRANSACTIONS Vol.48 No.9

<P>Three-dimensional analysis methods to calculate residual stress for functionally graded material (FGM) sample using sialon polytypoids to join silicon nitride and Alumina are introduced in this paper. The various multilayered FGM samples with 3, 9, and 20 layers were sintered to fabricate a crack-free joining of heterogeneous ceramics. To calculate three-dimensional thermal stresses of those fabricated FGM samples, a finite element analysis tool, ALGOR, was used. The Von Mises failure criterion and the maximum stress criterion were applied to predict failures in the FGM samples. For each case, calculated strength of each FGM layer by rule of mixture was compared with predicted thermal residual stresses. The Von Mises failure criterion predicted the locations of cracks more precisely than the maximum stress criterion. Such analyses are especially useful for graded FGM samples where the residual stresses are very difficult to measure experimentally.</P>

COAL COMBUSTION CHARACTERISTICS IN A CIRCULATING FAST FLUIDIZED BED

Lee, Geun Seong,Han, Gui Young,Kim, Sang Done 한국화학공학회 1984 Korean Journal of Chemical Engineering Vol.1 No.1

Preparation of platinum and palladium nanotubes using

Lee, Yong Geun,Oh, Chul,Park, Jae Hyung,Koo, Sang Man,Oh, Seong Geun THE KOREAN SOCIETY OF INDUSTRIAL AND ENGINEERING 2007 JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY -S Vol.13 No.2