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ZrO<sub>2</sub>-C계 침지노즐 제조시 상대습도에 따른 바인더용 페놀수지의 영향
윤상현,김장훈,김주영,이희수,구영석,Yoon, Sang-Hyeon,Kim, Jang-Hoon,Kim, Ju-Young,Lee, Hee-Soo,Koo, Young-Seok 한국세라믹학회 2011 한국세라믹학회지 Vol.48 No.4
The thermodynamic behavior of phenolic resin was investigated to verify the relation between the properties of porous ceramics with $ZrO_2$-C system for submerged entry nozzle and the characteristics of phenolic resin with various relative humidity. The green and the sintered density were decreased between 25% and 50% relative humidity, whereas they were gradually enhanced above 50% relative humidity. The highest value of apparent porosity was 20.1% and the minimum compressive strength was 69MPa in the specimen using the powder exposed to 50% relative humidity. As a result of thermal analysis for phenolic resin, the shift of endothermic peak to low temperature and the reduction of exothermic peak were observed, and the peaks corresponded to melting and curing of phenolic resin, respectively. The melting and the curing of phenolic resin generate the change of green density, and it can affect the properties of submerged entry nozzle.
WO<sub>3</sub> 첨가에 의한 TiO<sub>2</sub>계 SCR 촉매의 상전이 및 입자성장이 고온안정성에 미치는 영향
윤상현,김장훈,신병길,박삼식,신동우,이희수,Yoon, Sang-Hyeon,Kim, Jang-Hoon,Shin, Byeong-Kil,Park, Sam-Sik,Shin, Dong-Woo,Lee, Hee-Soo 한국결정성장학회 2011 韓國結晶成長學會誌 Vol.21 No.4
$WO_3$ 첨가가 $TiO_2$계 SCR 촉매의 고온안정성에 미치는 영향을 구조적, 형상학적 분석을 통해 규명하였다. 순수한 $TiO_2$시편과 10 wt%의 $WO_3$를 첨가한 $WO_3-TiO_2$ 시편을 제조하여 $800^{\circ}C$에서 5시간 동안 열적 스트레스를 인가하였다. FT-IR을 이용하여 촉매의 산점 변화를 확언한 결과 $WO_3-TiO_2$ 시편의 경우가 순수한 $TiO_2$ 시편에 비해 열적 열화로 인한 산점의 감소가 상대적으로 적었다. 반면 $WO_3-TiO_2$ 와 $TiO_2$의 anatase에 서 rutile로의 상전이 정도는 각각 28.4%와 22.9%로 오히려 $WO_3-TiO_2$ 시편에서 rutile 상이 더 많이 증가한 것을 확인하였다. 형상학적 분석 결과 $WO_3-TiO_2$ 시편은 고온에서 $TiO_2$에 고용되어 있던 amorphous 상태의 $WO_3$가 $TiO_2$ 입자 표면에 석출되며 결정화가 일어나게 되고 이로 인해 촉매의 입자성장을 억제함을 확인하였다. 따라서 SCR용 $TiO_2$ 촉매에 첨가된 $WO_3$는 anatase에서 rutile로의 상전이를 촉진시켜 고온에서의 촉매 활성을 저하시킬 수 있지만, 입성장 억제에 대한 영향이 커 결과적으로 고온안정성을 향상시킴을 확인하였다. Thermal stability of the $TiO_2$ SCR catalyst with W03 loading was investigated in terms of structural and morphological analyses. The $TiO_2$ catalysts with 10 w% $WO_3$ content and without $WO_3$ were prepared. which were heat-treated at $800^{\circ}C$ for 5 h. It was found that the catalytic acidity was decreased by thermal degradation in the $WO_3-TiO_2$ specimen that relatively less than the $TiO_2$ specimen from FT-IR analysis. The phase transition of the $TiO_2$ catalyst from anatase to rutile was increased by heal-treatment, and the percentage of the rutile phase was 28.4 % in the $WO_3-TiO_2$ and 22.9 % in the $TiO_2$. A shell region of $WO_3$ distinguished from a $TiO_2$ particle was also observed in the grain boundary region, and the $WO_3$ led to the suppression of grain growth. It could be confirmed that the suppression of grain growth can contribute to the improvement of catalytic properties for thermal stability more than the increase of anatase-rutile phase transformation which cause the reduction of the catalytic activity in the $TiO_2$ SCR catalyst by the presence of $WO_3$.
멀티플렉서와 5입력 다수결 게이트를 이용한 QCA RAM 셀의 분석 및 개선
윤상현(Sang-Hyeon Yoon)전준철(Jun-Cheol Jeon) 인문사회과학기술융합학회 2019 예술인문사회융합멀티미디어논문지 Vol.9 No.12
양자점 셀룰러 오토마타(QCA: Quantum-dot Cellular Automata)는 전력 소모, 속도, 그리고, 크기와 같은 점에서 CMOS를 대체할 새로운 회로로 주목받고 있다. QCA 환경에서 다양한 회로들이 제시되었으며, RAM 셀 또한 다양한 디자인이 제시되었다. 그 중에서 Asfestani 등이 제안한 멀티플렉서 기반의 RAM 셀과 Khosroshahy등이 제안한 5입력 다수결 게이트 기반의 RAM 셀은 크기, 에너지 소모, 지연시간, 그리고, 사용된 셀 수에서 다른 디자인들과 비교했을 때 더 좋은 성능을 보인다. 하지만, 올바르지 않은 출력이 나오는 경우가 존재한다. 본 논문에서는 해당 논문들이 제시한 RAM 셀 및 5입력 다수결 게이트에서 올바르지 않은 출력이 나오는 원인을 분석하고 이를 수정하여 정상적인 출력이 나오도록 개선한다. 두 회로는 각각 너무 짧은 배선의 길이와 잘못된 클록 지정이라는 문제점을 가지고 있고, 이를 개선하여 수정한 디자인을 실험한 결과 올바른 출력이 나오는 것을 확인하였으며, 개선된 회로들은 차후 더 큰 회로를 구성하는데 유용하게 사용될 수 있을 것이다. Quantum-dot Cellular Automata (QCA) is attracting attention as a new circuit to replace CMOS in terms of power consumption, speed and size. Various circuits have been presented in the QCA environment, and RAM cells have also been presented with various designs. Among them, the multiplexer-based RAM cell proposed by Asfestani et al. and the majority gate-based RAM cell proposed by Khosroshahy et al. have an advantage over other designs in size, energy consumption, latency and number of cells used. However, there are cases where incorrect output is produced. Therefore, in this paper, we analyze the cause of incorrect output from the RAM cell and 5-input majority gate presented by the papers, and correct it to improve the normal output. The two circuits each had problems with too short wire lengths and incorrect clock assignments, and we improved and simulated the modified design to ensure that the correct outputs are produced and improved circuits may later be usefully used to construct larger circuits.
연속주조용PorousNozzle의기공율이내구성에미치는영향
윤상현 ( Sang Hyeon Yoon ),이희수 ( Hee Soo Lee ),조문규 ( Mun Kyu Cho ),정두화 ( Doo Hoa Jeong ) 대한금속재료학회 ( 구 대한금속학회 ) 2010 대한금속·재료학회지 Vol.48 No.7
This study investigates the effects of porosity on the thermal stability and the thermal shock resistance of a porous nozzle used for blowing an inert gas. The samples of Al2O3-SiO2-ZrO2 system, which had the apparent porosity of 16~30% and bulk density of 2.6~3.2 g/cm3, were prepared by adding different graphite contents (5, 10, 20 wt%) as a pore-forming agent. The thermal shock test was conducted at ΔT=500, 1000, and 1400℃ also and the thermal stability was also carried out at 1550, 1600, and 1650℃ for 5 hrs. The specimen contained 10 wt% graphite had uniform pore size distribution, whereas the specimen with 20 wt% graphite showed non-uniform pore size distribution. As a result of thermal shock test, the specimen containing 10 wt% graphite appears to have higher mechanical strength than the other specimens (5, 20 wt% graphite). Both the 5 wt% and 20 wt% graphite specimens developed a non-uniform pore size distribution and cracks that were generated by intensive thermal stress.
시판 횟감어류에서의 Vibrio parahaemolyticus 분포 및 항생제 감수성에 관한 연구
성창현 ( Chang Hyeon Sung ),천정환 ( Jeong Hwan Cheon ),현지연 ( Ji Yeon Hyeon ),황인균 ( In Gyun Hwang ),곽효선 ( Hyo Sun Kwak ),윤상현 ( Sang Hyeon Yoon ),이정수 ( Jeong Soo Lee ),정윤희 ( Yun Hee Chung ),송광영 ( Kwang Young 한국수의공중보건학회 2010 예방수의학회지 Vol.34 No.3
Vibrio parahaemolyticus (V. parahaemolyticus) has been recognized as a significant food-borne pathogen around the world. In this study, we investigated the prevalence and antimicrobial resistance of V. parahaemolyticus isolated from raw fishes. A total of 64 samples of raw fishes purchased from a traditional seafood market in Seoul, Korea. were examined for the presence of V. parahaemolyticus using intestines, gills, and fins. Twenty five grams of all samples were enriched in 225ml of alkaline peptone water at 37℃ for 24h and then streaked onto thiosulfate citrate bile sucrose agar. Suspected colonies were inoculated into triple sugar iron agar for biochemical screening test and were finally confirmed with API 20NE strip. Antimicrobial resistance tests were performed with disc diffusion method in accordance with National Committee for Clinical Laboratory Standard. Thirty three V. parahaemolyticus strains were isolated from raw fishes among 33 out of 64 (51.6%). Among 33 isolates, 16 isolates (48.5%) were resistant to ampicillin, 7 isolates (21.2%) were resistant to amikacin, and all isolates were not resist to other antibiotics such as amoxicillin & clavulanic acid, sulfamethoxazole & trimethopenem, ciprofloxacin, cefotaxime and cefepime. Although the prevalence of V. parahaemolyticus was high in raw fishes compared to other studies, antimicrobial resistance rate of the isolates was relatively low. These results could be useful information for risk assessment of V. parahaemolyticus in raw fishes.