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원전 해체시 두께 50 mm 스테인리스강의 수중 레이저 절단시 보조가스 압력에 따른 드로스 양의 변화
김관,송무근,이수진,신동식,김종도 대한용접·접합학회 2021 대한용접학회 특별강연 및 학술발표대회 개요집 Vol.2021 No.11
레이저 절단시 레이저광으로 피가공물을 용융하고 용융물을 보조가스로 배출하는 작용이 연속적으로 일어나면서 절단이 진행된다. 용융금속을 절단홈 내에서 자연스럽게 배출시키지 못하는 경우 피가공물 이면에 드로스가 부착된다. 드로스는 원전 해체시 절단 공정에서 발생하는 2차 폐기물이며 방사성 오염 물질이므로 최소화하여야 한다. 절단홈 내부에서 용융된 금속의 배출상태가 양호하면 절단면의 품질이 우수하고, 가공부 이면에 드로스가 부착되는 것도 방지할 수 있다. 따라서, 본 연구에서는 후판 스테인리스강의 수중 레이저 절단시 보조가스 압력에 따른 질량 손실과 드로스 양의 변화를 확인하였다. 두께 50mm STS304L 스테인리스강을 4~15 bar의 보조가스 압력으로 변화시키면서 9 kW의 레이저 출력으로 절단하였다. 실험 전후 시험편의 무게 변화를 통해 질량 손실을 도출했으며, 부착된 드로스를 제거 후 무게를 측정하여 드로스 양을 구하였다. 결과적으로 보조가스 압력 8 bar의 조건에서 질량 손실은 많았으나 부착된 드로스의 양이 가장 적었다. 가스압력이 상승하면서 드로스 부착량이 증가하는 경향을 나타내는데 이는 보조가스에 의한 드로스의 냉각효과에 기인하는 것으로 판단 된다.
김관,윤한교,김성곤,이신영,Kim, Kwan,Yoon, Han-Kyo,Kim, Sung-Kon,Lee, Shin-Young 한국식품과학회 1987 한국식품과학회지 Vol.19 No.4
칡 전분 화화액(4, 5, 6 및 7%)의 리올로지적 성질은 측정온도 $30{\sim}66^{\circ}C$에서 지수법칙에 따랐으며, 의가소성 유동거동을 보였다. 유동거동 지수는 측정온도에 대하여는 거의 비슷한 값을 보였으나, 농도의 증가에 따라 다소 감소하여 의가소성 경향이 증가하였다, 그러나 점조도 지수는 농도의 증가에 따라 증가하였으며, 측정온도에 대하여는 반대의 경향을 보였다. 칡 전분 호화액의 겉보기 점도는 농도의 증가에 따라 지수함수적으로 증가하였고, 활성화에너지는 $4.068{\sim}4.542kcal/mole$이었다. The rheological properties of gelatinized arrowroot stach solution $(4{\sim}7%)$ followed the power law and showed a pseudoplastic behavior at the temperature range of $30{\sim}66^{\circ}C$. The flow behavior index was essentially remained constant at all temperatures, but decreased as starch concentration increased. The consistency index was exponentially increased with the increase of starch concentration. The activation energy of flow of gelatinized starch solution was $4.068{\sim}4.542\;kcal/mole$.
김관,Jeong-Yong Choi,신권수 대한화학회 2013 Bulletin of the Korean Chemical Society Vol.34 No.3
A few years ago, the plasmon-induced electronic coupling (PIEC) model was proposed in the literature to explain small changes in the surface-enhanced Raman scattering (SERS) in nanogap systems. If this model is correct, it will be very helpful in both basic and application fields. In light of this, we carefully reexamined its appropriateness. Poly(4-vinylpyridine) (P4VP) used in the earlier work was, however, never a proper layer, since most adsorbates not only adsorbed onto Ag nanoparticles sitting on P4VP but also penetrated into the P4VP layer deposited initially onto a flat Ag substrate, ultimately ending up in the SERS hot sites. Using 1,4- phenylenediisocyanide and 4-nitrophenol as the affixing layer and the foreign adsorbate, respectively, we could clearly reveal that the PIEC model is not suited for explaining the Raman signal in a nanogap system. Most of the Raman signal must have arisen from molecules situated at the gap center.
Low-resistance ohmic contacts to p-$Hg_{0.7}$$Cd_{0.3}$Te
김관,정한,김성철,이희철,김충기,김홍국,김재묵,Kim, Kwan,Chung, Han,Kim, Sung-Chul,Lee, Hee-Chul,Kim, Choong-Ki,Kim, Hong-Kook,Kim, Jae-Mook The Institute of Electronics and Information Engin 1994 전자공학회논문지-A Vol.31 No.10
Ohmic contacts between Au and p-HgHg_{0.7}Cd_{0.3}Te$ with low specific contact resistance have been obtained. The contact region of the wafer is first pre-heated for 5 seconds in a rapid thermal processing equipment. The temperature reaches a maximum value of about 200$^{\circ}C$ at the end of the 5 seconds. Next, a thin Au film is formed on the contact region by immersing the sample in AuCl$_{3}$ solution. the sample is then post-annealed in the same condition as the pre-heating after Pb/In pad metals are deposited on the electroless Au contacts. The specific contact resistance measured by transmission line model is 5${\times}10^{-3}{\Omega}cm^{2}$ at 80K. RBS and differential Hall measurement data suggest that the above low resistance ohmic contact is ascribed to surface traps and increased gold diffusion rate.
김관,최정용,신동하,이향봉,신권수 대한화학회 2011 Bulletin of the Korean Chemical Society Vol.32 No.8
A nanogap formed by a metal nanoparticle and a flat metal substrate is one kind of “hot site” for surface-enhanced Raman scattering (SERS). The characteristics of a typical nanogap formed by a planar Au and either an Au and Ag nanoparticle have been well studied using 4-aminobenzenethiol (4-ABT) as a probe. 4-ABT is, however, an unusual molecule in the sense that its SERS spectral feature is dependent not only on the kinds of SERS substrates but also on the measurement conditions; thus further characterization is required using other adsorbate molecules such as 1,4-phenylenediisocyanide (1,4-PDI). In fact, no Raman signal was observable when 1,4-PDI was selfassembled on a flat Au substrate, but a distinct spectrum was obtained when 60 nm-sized Au or Ag nanoparticles were adsorbed on the pendent –NC groups of 1,4-PDI. This is definitely due to the electromagnetic coupling between the localized surface plasmon of Au or Ag nanoparticle with the surface plasmon polariton of the planar Au substrate, allowing an intense electric field to be induced in the gap between them. A higher Raman signal was observed when Ag nanoparticles were attached to 1,4-PDI, irrespective of the excitation wavelength, and especially the highest Raman signal was measured at the 632.8 nm excitation (with the enhancement factor on the order of ~10^3), followed by the excitation at 568 and 514.5 nm, in agreement with the finite-difference timedomain calculation. From a separate potential-dependent SERS study, the voltage applied to the planar Au appeared to be transmitted without loss to the Au or Ag nanoparticles, and from the study of the effect of volatile organics, the voltage transmission from Au or Ag nanoparticles to the planar Au also appeared as equally probable to that from the planar Au to the Au or Ag nanoparticles in a nanogap electrode. The response of the Au-Ag nanogap to the external stimuli was, however, not the same as that of the Au-Au nanogap.