• Journal of Welding and Joining
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• 제35권1호
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• pp.89-94
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• 2017

The microstructure and dilatation for 0.15C steels were investigated to define the phase transformation during the quenching and partitioning (Q&P) process. For the one step Q&P dilatation, the isothermal martensite/bainite transformation occurred because the holding temperature was between $M_s$ and $M_f$. The isothermally transformed martensite/bainite and the athermally transformed martensite were produced by a loss of retained austenite. As the holding time increased, new martensite-start ($M_s$) temperature produced from the final quenching process decreased due to the carbon partitioning from the martensite to the retained austenite. This was the direct evidence of increment for the retained austenite stability. For the two step Q&P dilatation, the isothermal bainitic transformation occurred because the partitioning temperature was larger than the $M_s$ and new $M_s$. The partitioning at $400^{\circ}C$ indicated the short incubation period for the bainite transformation than the $350^{\circ}C$ partitioning because the partitioning at $400^{\circ}C$ should acquire the larger thermal driving force for carbon partitioning than the $350^{\circ}C$ partitioning. A quick drop of $M_s$ and short period of bainite incubation for the $400^{\circ}C$ partitioning steel were also the direct evidence of significant effects of carbon partitioning on the stability of retained austenite.

• 한국결정성장학회지
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• 제28권5호
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• pp.206-210
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• 2018

에나멜 기법을 활용하여 Ti6Al4V 합금에 두 종류의 생체활성화 유리를 코팅하였다. 재료간의 열팽창계수 차이에 의한 열응력을 줄이기 위해 재료간의 열팽창계수의 차가 $2{\times}10^{-6}/^{\circ}C$ 정도 되도록 생체활성화 유리 조성을 선정하였다. 열팽창계수의 차이에도 불구하고 Ti6Al4V 합금과 코팅 유리간에 확산결합에 의해 양호한 부착이 형성되었음을 FE-SEM과 EDS 분석으로 확인하였다. 의사체액에 담근 후 코팅 표면에 일반적인 생체활성화 유리와 같은 hydroxycarbonate apatite가 형성됨을 FT-IR로부터 확인하였다.

• 한국전기전자재료학회논문지
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• 제19권7호
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• pp.605-610
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• 2006

We have investigated $Al_{0.25}Ga_{0.75}As/In_{0.2}Ga_{0.8}As$ structures for pseudomorphic high electron mobility transistor(pHEMT), which were grown by molecular beam epitaxy(MBE) and consequently annealed by rapid thermal anneal(RTA), using Hall measurement, photoluminescence, and transmission electron microscopy (TEM). According to intensity and full-width at half maximum maintained stable at the same energy level, the quantized energy level in $Al_{0.25}Ga_{0.75}As/In_{0.2}Ga_{0.8}As$ quantum wells was independent of the RTA conditions. However, the Hall mobility was decreased from $6,326cm^2/V.s\;to\;2,790cm^2/V.s\;and\;2,078cm^2/V.s$ after heat treatment respectively at $500^{\circ}C\;and\;600^{\circ}C$. The heat treatment which is indispensable during the fabrication procedure would cause catastrophic degradation in electrical transport properties. TEM observation revealed atomically non-uniform interfaces, but no dislocations were generated or propagated. From theoretical consideration about the mobility changes owing to inter-diffusion, the degraded mobility could be directly correlated to the interface scattering as long as samples were annealed below $600^{\circ}C$ lot 1 min.

• 한국식물병리학회지
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• 제1권1호
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• pp.33-37
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• 1985

황록색줄무늬모자익과 줄기 정단부가 구부러지는 증상을 보이는 대두 이병주를 채집하여 지표식물검정, 충매전염, 물리적 성질 조사, 항혈청검정 및 전자현미경검경을 하였다. 지표식물검정결과 T. expansa와 Scotia에 국부병반반응, 동부, 완두, 명아주 등에 전신감염 증상을 일으켰다. 복숭아혹진딧물에 의한 전염율은 $90\%$였다. 물리적 성질은 내열성이 $60^{\circ}C$, 내희석성이 1,000배였고, 내보존성이 2일이었다. 바이러스를 순화하여 항혈청제조결과 1:1024의 역가를 보였으며 일본 바이러스연구소에서 분양 받고 AMV 항혈청과 양성반응을 보였다. 전자현미경검경 결과 대부분 길이가 60nm인 박테리아 모양의 바이러스 입자가 검경되었다.

• 천문학회지
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• 제43권2호
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• pp.25-39
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• 2010

We perform kinetic simulations of diffusive shock acceleration (DSA) in Type Ia supernova remnants (SNRs) expanding into a uniform interstellar medium (ISM). Bohm-like diffusion due to self-excited $Alfv\acute{e}n$ waves is assumed, and simple models for $Alfv\acute{e}nic$ drift and dissipation are adopted. Phenomenological models for thermal leakage injection are considered as well. We find that the preshock gas temperature is the primary parameter that governs the cosmic ray (CR) acceleration efficiency and energy spectrum, while the CR injection rate is a secondary parameter. For SNRs in the warm ISM of $T_0\lesssim10^5K$, if the injection fraction is $\xi\gtrsim10^{-4}K$, the DSA is efficient enough to convert more than 20% of the SN explosion energy into CRs and the accelerated CR spectrum exhibits a concave curvature flattening to $E^{-1.6}$, which is characteristic of CR modified shocks. Such a flat source spectrum near the knee energy, however, may not be reconciled with the CR spectrum observed at Earth. On the other hand, SNRs in the hot ISM of$T_{0}\approx10^{6}K$ with a small injection fraction, $\xi$<$10^{-4}$, are inefficient accelerators with less than 10% of the explosion energy getting converted to CRs. Also the shock structure is almost test-particle like and the ensuing CR spectrum can be steeper than $E^{-2}$. With amplified magnetic field strength of order of $30{\mu}G$ $Alfv\acute{e}n$ waves generated by the streaming instability may drift upstream fast enough to make the modified test-particle power-law as steep as $E^{-2.3}$, which is more consistent with the observed CR spectrum.

• 한국결정성장학회지
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• 제4권1호
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• pp.63-70
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• 1994

초이온도전체 ${\beta}-Ag_3SI$ 단결정을 AgI와 $AG_2S$의 혼합물을 반응시켜서 열처리하여 얻었다. 성장시킨 단결정은 직경 $200{mu}m$ 정도의 구상으로 성형시켰다. 실온에서 X-선 단결정 해석법을 이용하여 정밀한 결정구조 해석을 행했다. 이들 결정구조의 해석결과 ${\beta}-Ag_3SI$의 $Ag^+$는 6-배위의 3c자리보다 4-배위의 12h자리에 점유함이 밝혀졌다. $Ag^+$의 확률밀도분포(probabilty density function)로 부터 [110]방향에서 $Ag^+$의 one-particle potential(o.p.p.)을 계산하였다.${beta}-Ag_3SI$ 구조의(001)면에서 $Ag^+$가 확산에 필요한 활성화에너지는 0.012eV라는 것이 o.p.p.곡선에 의해 계산되었다.

• 에너지공학
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• 제8권2호
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• pp.248-255
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• 1999

미분형 고정층 반응기에서 고체산 촉매(HY 제올라이트, $\beta$-제올라이트, HZSM-5)를 이용하여 폐윤활유를 1차 열분해한 오일의 촉매분해 반응을 연구하였다. 촉매의 활성 검토에 사용된 원료물질은 폐윤활유를 반응온도 48$0^{\circ}C$, 반응시간($\tau$) 60분으로 진행되는 벤치규모의 연속공정에서 생산된 제품이다. HY제올라이트의 경우 탄소수 21개 이하의 경유 성분을 얻을 수 있는 최적 반응조건은 WHSV(weight hourly space velocity)=1, 반응온도는 375$^{\circ}C$임을 알 수 있었다. 암모니아 탈착법을 이용하여 전체의 산점 및 강산점 수를 측정한 결과 $\beta$-제올라이트가 가장 많은 것으로 나타났다. 탄소수 21개 이하 성분의 수율을 기준으로 촉매의 활성 순서를 평가할 때 HY제올라이트〉$\beta$-제올라이트〉HZSM-5 임을 알 수 있었다. 또한 코크의 생성량 역시 동일한 순서를 보였다. 이러한 결과를 보인점은 HY제올라이트의 경우 촉매내부 미세기공의 평균직경이 크므로. 반응물이 촉매내부로 쉽게 확산될 수 있어 내부의 산점에서 분해반응의 진행이 적절함으로 나타난 결과로 판단되었다. 이러한 점은 코크의 생성량으로도 확인할 수 있었다.

• Journal of Mechanical Science and Technology
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• 제20권12호
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• pp.2218-2229
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• 2006

A conservative finite-volume numerical method for unstructured grids with the cell-centered method has been developed for computing flow and heat transfer by combining the attractive features of the existing pressure-based procedures with the advances made in unstructured grid techniques. This method uses an integral form of governing equations for arbitrary convex polyhedra. Care is taken in the discretization and solution procedure to avoid formulations that are cell-shape-specific. A collocated variable arrangement formulation is developed, i.e. all dependent variables such as pressure and velocity are stored at cell centers. For both convective and diffusive fluxes the forms superior to both accuracy and stability are particularly adopted and formulated through a systematic study on the existing approximation ones. Gradients required for the evaluation of diffusion fluxes and for second-order-accurate convective operators are computed by using a linear reconstruction based on the divergence theorem. Momentum interpolation is used to prevent the pressure checkerboarding and a segregated solution strategy is adopted to minimize the storage requirements with the pressure-velocity coupling by the SIMPLE algorithm. An algebraic solver using iterative preconditioned conjugate gradient method is used for the solution of linearized equations. The flow analysis code (PowerCFD) developed by the present method is evaluated for its application to several 2-D structured-mesh benchmark problems using a variety of unstructured quadrilateral and triangular meshes. The present flow analysis code by using unstructured grids with the cell-centered method clearly demonstrate the same accuracy and robustness as that for a typical structured mesh.

• 한국의류학회지
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• 제11권3호
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• pp.41-55
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• 1987

The purpose of this study is to investigate the effects of napping of knitted fabric on wear sensation and physiological responses. Experimental garments were four types of warm-ups made of either $100\%$ PET or $65/35\%$ P /C and either napped or unnapped respectively. Two healthy young female adults were chosen as subjects for the experiment. Experimental room conditions were as follows: Temp., $22\pm0.5^{\circ}C$ R.H., $54\pm3\%$ and Air Velocity, 0.25m/ sec or 2. 86m/sec. The subjects exercised on bicycle ergometer and rested alternatively for totally 45-min. The results are summarized as follows. 1) With napped Warm-up, chest, back, mean skin temp. and microclimates, i.e., temp., relative humidity and water vapor pressure inside the clothing, were higher than with unnapped warm-up. And there was no difference in pulse rate between napped and unnapped warm-ups. 2) Wear sensations of thermal, humidity, tactile and comfort were 'more hot' and 'more uncomfortable' in 0.25m/sec air velocity. but in 2.86m/sec condition the tactile sensation was 'better' and 'more comfortable' with napped warm-ups. According to Pearson's Correlation, among various kinds of wear sensations, tactile is most related with comfort. From these results, it can be concluded that napped fabric decreases the rate of heat trans? mission and moisture diffusion through the clothing. Therefore skin and body temp. and temp., R.H., Vapor Pressure inside the clothing are increased.

• The Plant Pathology Journal
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• 제22권1호
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• pp.51-62
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• 2006

Three strains of Cucumber mosaic virus (CMV) have been found to cause a lethal disease, referred to as fern leaf syndromes and mild mosaic symptoms in tomato (Lycopersicon esculentum Mill.) crops grown in Kuwait. CMV strains were detected and identified based on host range, symptomatology, serology, electron microscopy, and ribonucleic acid (RNA) electrophoresis in polyacrylamide gels. A high degree of viral genomic heterogeneity was detected among CMV strains isolated in Kuwait, with no apparent correlation to symptomatology in tomato host plants. Two different virus satellites of 'CMV associated RNA 5', designated CARNA 5, were detected in two virus strains that caused both lethal disease and mild symptoms, designated CMV-D1 and CMV-S1 respectively. CARNA5 was not detected in the third CMV strain that caused fern leaf syndromes designated CMV-F. All the three isolated strains were serologically indistinguishable from each other and may belong to one serotype according to Ouchterlony gel diffusion tests. These strains transmitted via aphids (Myzus persicae Sulz) in a non-persistent manner. Physical properties of the virus strains were very similar where thermal inactivation test showed that virus withstood heating for 10 min at $70^{/circ}$, dilution end point was $10^{-4}$, and the longevity in vitro at room temperature was less than 5 days for all virus strains. CMV-D1 and CMV-F were the most devastating diseases spreading in both greenhouse and field-grown tomato where aborted flower buds failed on fruit setting due to the viral infection. This is the first report to isolate three different strains of CMV in Kuwait.