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최동욱,박병기,한명완,Choe, Dong-Uk,Park, Byung-Ki,Han, Myung-Wan 한국세라믹학회 2007 한국세라믹학회지 Vol.44 No.10
To precipitate the complex gels of the pH 6, 7, 8, 9 included in a flux and an aluminum hydroxides gel, an aqueous solution of a mixture of $Na_2CO_3\;and\;Na_2PO_4{\cdot}12H_2O$ was added with stirring in an aqueous solution of a mixture of $Al_2(SO_4){_3}{\cdot}18H_2O,\;Na_2SO_4\;and\;K_2SO_4$, and then the complex gels were aged in 20 h at $90^{\circ}C$. As the hydrolysis pH changed, it had an effect on the physical properties such as the crystal structure, crystal morphology and a phase transition temperature of the AlO(OH) gel, and also on the crystal structure, crystal morphology, particle size and particle size distribution of the ${\alpha}-Al_2O_3$ platelets prepared by molten-salt precipitation. Also, in this study, the complex gels were crystallized at $1,200^{\circ}C$ and thereafter dried at $110^{\circ}C$, and then it was investigated to effect of the hydrolysis pH on the crystal structure, morphology and particle size distribution of the ${\alpha}-Al_2O_3$ platelets crystals using XRD, DTA, SEM and particle size analyzer.
차세대 이동통신 시스템에서 유동적 USIM 카드를 이용한 인증 시스템
최동욱,황재영,정연호,Choi, Dong-Wook,Hwang, Jae-Young,Chung, Yeon-Ho 한국정보통신학회 2011 한국정보통신학회논문지 Vol.15 No.11
본 논문은 유동적 USIM(Universal Subscriber Identity Module)을 이용한 사용자 편의를 위한 인증시스템을 제안한다. 유동적 USIM 카드는 이동통신망 이용자에게 시스템에서 단말의 할당된 고유번호나 주민등록번호와 같은 개인화 정보를 인증의 인자로 이용하여 제한된 횟수나 사용시간을 허가하는 인증 방법이다. 본 연구에서 제안하는 모듈을 검증하기 위해 시뮬레이션을 수행하였으며 제안한 알고리즘 및 시스템이 현재의 시스템에서 완벽하게 동작하며, 기존의 USIM 카드를 사용하는 인증방법과도 높은 호환성을 확인하였다. 또한 유동적 USIM 카드를 이용하여 또 다른 인증방식을 설계할 수도 있음을 제시하였다. 제안하는 유동적 USIM 기술을 적용할 경우 간단하면서도 강력한 인증방법과 시스템을 개발할 수 있을 것이며 사용자 환경과 독립적으로 이동통신망 접근을 가능하게 해 줄 수 있다. This paper presents a user-friendly authentication system using a flexible USIM. In the proposed method and its system, the flexible USIM utilizes personalized data such as Mobile Directory Number(MDN) and social security number as the key to user authentication. The authentication method proposed in this paper permits limited times of use and/or limited duration of use. A simple simulation model shows that the proposed algorithm works well and shows high compatibility with existing authentication methods. In addition, an alternative or more advanced authentication system can be developed with the proposed flexible USIM card. It is seen that this simple alternative method will eventually be able to make wireless communication networks more easily accessible for subscribers, irrespective of user environments.
황산알루미늄의 가수분해에 의해 석출된 AlO(OH) 겔의 숙성시간이 판상 α-Al<sub>2</sub>O<sub>3</sub>의 결정성장에 미치는 영향
최동욱,박병기,서정권,이정민,Choe, Dong-Uk,Park, Byung-Ki,Suh, Jeong-Kwon,Lee, Jung-Min 한국세라믹학회 2006 한국세라믹학회지 Vol.43 No.9
To precipitate the complex gel of flux and aluminum hydroxides gel, aqueous solution of the mixture of $Na_2CO_3\;and\;Na_2PO_4{\cdot}12H_2O$ was added with stirring in aqueous solution of the mixture of $Al_2(SO_4)_3{\cdot}14{\sim}18H_2O,\;Na_2SO_4$, and then the complex gel was aged in $0{\sim}30h\;at\;90^{\circ}C$. As aging time passed, the aluminum hydroxides was grown into the acicular AlO(OH) gel. Also, aging time had an effect on physical properties of the AlO(OH) gel and on crystal growth of the flaky ${\alpha}-Al_2O_3$ prepared by molten-salt precipitation. In this study, the complex gel was crystallized in temperature range of $400{\sim}1,200^{\circ}C$ after drying at $110^{\circ}C$, and then it was investigated to effect of aging time on precipitation temperature, size, thickness, morphology and particle size distribution of the flaky ${\alpha}-Al_2O_3$ crystal. As aging time passed, the flaky a${\alpha}-Al_2O_3$ crystal showed a tendency toward an increase in size and thickness as result from an increase in BET surface area and pore volume of the acicular AlO(OH) gel.
최동욱,김준철,김근영,안철,Choi, Dong-Wook,Kim, Jun-Chul,Kim, Geun-Young,An, Chul The Institute of Electronics and Information Engin 1992 전자공학회논문지-A Vol.29 No.11
The dependence of electrical characteristics of RuO$_2$-based thick film resistors on the RuO$_2$ contents, glass composition variation and the firing temperatures was measured. The sheet resistance of resistors decreased as the contents of RuO$_2$ increased and at firing temperatures higher than C, the sheet resistance increased as the firing temperature increased. In case of using lead borosilicate glass-containing $Bi_{2}O_{3}$, the sheet resistance decreased as the contents of $Bi_{2}O_{3}$ increased. TCR changes from negative to positive values as RuO$_2$ contents increased and from positive to negative values as the firing temperature increased. TCR increased to positive values as $Bi_{2}O_{3}$ increased in the glass.
생물막 공정에서 질소제거효율 향상을 위한 유기성담체의 효용성 검토
최동욱,최영균,김대영,김윤중,정태학 대한상하수도학회 2003 상하수도학회지 Vol.17 No.3
Availability of organic media for improving nitrogen removal efficiency in a biofilter process was studied. Although, aerobic and anoxic phase could be clearly divided during the operation of single-stage biofilter process and nitrification efficiency was about 80%, denitrification efficiency was very low due to depletion of organic substrate in anoxic phase. However, the deficiency could be improved by addition of organic media in anoxic phase from the simulated result. Nitrogen removal efficiency in a biofilter process packed with organic media in anoxic phase was predicted to be 29% higher than that packed with inorganic media. In addition, about 79% of nitrogen removal efficiency could be obtained from a column test using organic media innoculated by activated sludge. Improvement in nitrogen removal efficiency was responsible for organic leaching from the organic media and the leaching rate was 0.21㎎COD/g-org.media/day.
백내장수술 중 전방 내 증류수 관류된 환자의 치험 1예
최동욱,정인영,서성욱,송준경 대한안과학회 2004 대한안과학회지 Vol.45 No.2
Purpose: To report a case of anterior chamber irrigation with distilled water during cataract operation Methods: During the cataract operation of 56 year-old male patient, corneal edema and anterior chamber hazziness were noted after anterior chamber irrigation with distilled water for a minute. Distilled water was replaced rapidly balanced salt solution (BSS) as irrigation solution and operation was completed. At postoperative one day, corneal edema and anterior chamber exudative membrane were formed. After topical 5% NaCl, 1% prednisolone treatment, corneal edema and exudative membrane disappeared at postoperative sixth week. BCVA was 0.6. At postoperative ninth week, the patient complained of decreased visual acuity. On fundus exmination and flourescein angiography, cystoid macular edema (CME) was detected. Results: After prednisolone oral administration and diclofenac eyedrop instillation, CME improved. At postoperative 24th month, BCVA was 0.8 and CME disappeared. Conclusions: From our experience of a case of anterior chamber irrigation with distilled water during cataract operation, if balanced salt solution replaces hypotonic solution rapidly as irrigation solution, corneal and other complications are managed properly, long term visual acuity appears good. 목적 : 백내장수술 중 전방 내로 증류수가 관류된 환자에서 술후 24개월의 경과관찰을 보고하고자 한다. 대상과 방법 : 56세 남자환자가 백내장수술도중 초기 약 1분간 증류수 관류 후 술 중 각막부종 및 전방혼탁이 보여 평형염액(balanced salt solution)으로 관류액을 치환하여 수술을 마쳤다. 술 후 각막부종 및 전방 내 삼출성 막이 형성되었다. 5% NaCl 과 1% prednisolone 점안 등의 치료 후 각막부종 및 삼출성 막은 사라졌으며, 술 후 6주에 교정시력 0.6이었다. 술 후 9주에 시력저하 호소하여 시행한 안저검사 및 형광안저촬영검사상 낭포황반부종 소견을 보였다. 결과 : prednisolone 경구복용 및 diclofenac 점안 치료하였고, 낭포황반부종은 좋아졌으며 술 후 24개월 경과관찰 시 교정시력은 0.8, 낭포황반부종 소견은 보이지 않았다. 결론 : 백내장수술 중 전방 내로 증류수가 관류된 환자에서 신속히 평형염액으로 관류액을 치환하고 합병증에 대한 적절한 치료시 장기적으로 좋은 시력예후를 보일 수 있었다.