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서희돈,이동원,손미정,최세곤 嶺南大學校 工業技術硏究所 1998 工業技術硏究所論文集 Vol.26 No.1
This paper describes structural characteristics of three kinds of piezoresistive pressure sensors, which include wheatstone-bridge type, center-boss type and single-element type, fabricated on one-chip by batch process. In order to optimize device dimensions with respect to the desired characteristics, analytical formula and finited-element modeling(FEM) are used in design process. In experiments the pressure sensitivity of wheatstone-bridge type is about 2.2㎷/V·㎪. The fabricated center-boss pressure sensor has improved in the characteristics as linearity at low pressure, and sensitivity is about 2.415㎷/V·㎪. In single-element type with a four-terminal gauge using shear stress, the maximum sensitivity about 0.4㎷/V·㎪ appeared at the center of the diaphragm with the 3:1 of the length : width ratio. this type is very appropriate method to minimize the temperature dependance of the offset voltage and sensitivity, because the fabricated sensors reduce the offset of themal stress and mismatch of piezoresistros as compared with the wheatstone-bridge type.
Structural Analysis of Open-Column Fractionation of Peracetic Acid-Treated Kraft Lignin1
( Se-Yeong PARK ),( June-Ho CHOI ),( Seong-Min CHO ),( Joon Weon CHOI ),( In-Gyu CHOI ) 한국목재공학회 2020 목재공학 Vol.48 No.6
This study investigates the selective fractionation of lignin with uniform structures and lower molecular weight. Lignin solubilization was first performed using a solution of acetic acid (AA) and hydrogen peroxide (HP) (4:1, (v/v)) to form peracetic acid (PAA), which is a strong oxidant. After the PAA-induced solubilization that occurred at 80°C, totally soluble lignin was extracted by ethyl acetate (EA) and divided into organic- and water-soluble fractions. The EA fraction was then fractionated by open-column using three solutions (chloroform-ethyl acetate, methanol, and water) sequentially. With an increase in the solvent polarity during the fractionation step, the molecular weight of the lignin-derived compounds in the fraction increased. Remarkably, some lignin fractions did not have aromatic structures. These fractions were identified as carboxylic acid-containing polymers like poly-carboxylates. These results conclude that the selective production of lignin-derived polymers with specific molecular weight and structural characteristics could be possible through open-column fractionation.
Corrosion and Soldering Behaviour of STD61 Coated by Arc Ion Plating Coatings
Choi, Se Weon,Kim, Young Chan,Kim, Cheol Woo,Cho, Jae Ik,Kang, Chang Seog Trans Tech Publications, Ltd. 2013 Advanced materials research Vol.813 No.-
<P>In order to investigate corrosion and soldering behaviour of STD61, TiN and TiAlN were coated on the surface of STD61 by using Arc Ion Plating. The structure of the coatings was examined as a function of deposition conditions by X-ray diffraction, and the crystallographic orientation was determined by use of a texture coefficient. TiN coating was grown with a strong (111) preferred orientation of a typical NaCl-type crystal structure. This strong (111) preferred orientation had been commonly observed from the TiN coatings deposited by physical vapour deposition techniques. TiAlN coatings, however, showed relatively multiple orientations mainly of (111) and (200). Furthermore, TiAlN film demonstrated superior corrosion resistance in a molten aluminum alloy at 680°C. This paper described in detail the corrosion and mass loss phenomena related to this steel-cast metal interaction.</P>
Effects of Mn and Ca Additions on Microstructure and Mechanical Properties of Al-Mg Alloy
Choi, Se Weon,Kim, Young Chan,Kang, Chang Seog,Jung, Jae Min,Hong, Sung Kil Trans Tech Publications, Ltd. 2013 Advanced materials research Vol.813 No.-
<P>The effects of Mn and Ca contents on the microstructure and mechanical properties in Al-Mg alloy were investigated. The results showed that mechanical properties of Al-4.5wt.%Mg were increased as Mn content was raised from 0.1 to 0.5wt.%. Thermodynamic analysis and FE-SEM observation showed that Al15(Fe,Mn)3Si2 phase began to form as Mn content exceeded 0.3wt.%. The case of Ca addition, the tensile strength and elongation of Al-4.5wt.%Mg were decreased as Ca content was increased from 0 to 3wt.%. The maximum solubility of Ca for Al is very lower to 0.074wt.%, the most of Ca precipitated in the form of Al2Ca phase which is very brittle and the increase of Ca content was reduced the mechanical properties.</P>
알루미늄 주조용 SKD61 금형강의 표면처리 방법에 따른 특성 평가
최세원 ( Se-weon Choi ),김철우 ( Cheol-woo Kim ),김용호 ( Yong-ho Kim ),유효상 ( Hyo-sang Yoo ) 한국열처리공학회 2021 熱處理工學會誌 Vol.34 No.6
Arc ion plating (AIP), laser cladding, and nitriding are methods that can prevent mold damage or repair and create cracks and breakages on the die surface. The dissolution and soldering behavior of coated SKD61 by using arc ion plating, laser cladding, and nitriding was investigated. The structure of the coating was investigated as a function of deposition conditions by X-ray diffraction and the crystallographic orientation was determined using the texture factor. The TiAlN film deposited with AIP showed excellent corrosion resistance in the molten aluminum alloy at 680℃. In this paper, we have detailed the corrosion and mass loss phenomena associated with these steel-cast metal interactions. (Received Septemer 23, 2021; Revised Septemer 30, 2021; Accepted October 12, 2021)
Catalytic conversion of hemicellulosic sugars derived from biomass to levulinic acid
Jeong, Hanseob,Park, Se-Yeong,Ryu, Ga-Hee,Choi, June-Ho,Kim, Jong-Hwa,Choi, Won-Sil,Lee, Soo Min,Choi, Joon Weon,Choi, In-Gyu Elsevier 2018 CATALYSIS COMMUNICATIONS - Vol.117 No.-
<P><B>Abstract</B></P> <P>Catalytic conversion of hemicellulosic sugars from biomass towards levulinic acid production was conducted using modified-zeolite Y (commercial). The zeolite was treated by NaOH of different concentration (x M) before used for the conversion of C5 sugars to levulinic acid. The modified zeolites had a larger porosity and an increased concentration of stronger acid sites compared to the untreated zeolite. Levulinic acid yield of 4.6% (conversion of C5 sugar to levulinic acid: 42.7%) was maximized at 190 °C and reaction time of 180 min (batch reactor), when using the zeolite treated with 0.25 M NaOH. In addition, with the absence of C6 sugar, the conversion of C5 sugar was higher than that of C5-C6 sugar mixture. The present work provides a new heterogeneous catalytic approach for levulinic acid production from liquid hydrolysates (by-product of biomass utilization).</P> <P><B>Highlights</B></P> <P> <UL> <LI> Hemicellulosic sugar was converted to levulinic acid (LA) using modified-zeolite. </LI> <LI> LA yield was the highest at 190 °C, 180 min, and 0.25 M NaOH-treated zeolite (AZ25). </LI> </UL> </P>
디지털 이미지 데이터의 저작권 보호를 위한 디지털 워터마킹 개발에 관한 연구
최종욱,조정석,유세근,김종원 한국데이타베이스학회 1999 공동학술대회 Vol.1 No.1
본 연구는 디지털 이미지 데이터에 대한 창작자의 저작권 보호 기술인 watermarking 기술을 연구하였다. 저작권 보호를 위한 정보를 invisible watermark로 삽입하였꼬, watermarking된 칼라 이미지를 데이터 압축, Filtering, cropping등과 같은 여러가지 외부 공격에 대한 내구성을 실험하였다. Invisible watermark를 삽입하기 위하여 변형된 주파수 변환기법을 이용하였으며, 기존의 PRN(pacudo random number)방법보다 가시성이 뛰어나 이미지 형태의 로고를 삽입하여 저작권에 대한 확증성을 제고하였다.
( Se Weon Kim ),( Seok Bae Kim ),( Il Han Song ),( Hong Ja Kim ),( Jung Eun Shin ),( Hyun Deok Shin ),( Jun Ho Choi ),( Ki Bae Bang ),( Kwang Woo Nam ),( Hyun Jin Baek ),( Byeong Wook Cho ) 대한간학회 2018 춘·추계 학술대회 (KASL) Vol.2018 No.1
Aims: A patient who has resolved acute hepatitis B and has produced anti-HBs acquires protective immunity against hepatitis B virus. However, reactivation of hepatitis B virus may occur if the patient is exposed to an immunocompromised state by using immunosuppressive drugs or chemotherapeutic agents because cccDNA can reside within hepatocytes after recovery from acute hepatitis B. Therefore, guidelines for hepatitis B recommend the use of prophylactic antiviral agents, such as entecavir and tenofovir, in patients with anti-HBc IgG. The reactivation of hepatitis B without exposure to an immunocompromised state is very rare, and only 1 case has been reported worldwide Methods: An 82-year-old male patient visited Dankook University Hospital because of high aspartate transaminase (AST), alanine aminotransferase (ALT) and total bilirubin levels. He had shown HBsAg negative/anti-HBs positive results when he underwent blood tests 1 year previously. However, the present blood test revealed HBsAg positive/anti-HBs negative findings and a high titer of HBV DNA (814,815 copies/mL). He underwent vertebroplasty 5 years previously and did not have any other medical history. Other blood and radiologic examinations failed to show other diseases that could affect host immunity. The patient started antiviral treatment with entecavir Results: Patient passed away because of deteriorated hepatic function and hepatorenal syndrome 20 days after admission. It is very rare that a patient with anti-HBs would have hepatic failure and pass away without trigger factors Conclusions: The present case showed that HBV reactivation in a patient with anti-HBs can develop without trigger factors. This kind of reactivation is very rare, and only one case has been reported until now. We hope that the present case will be helpful for understanding HBV reactivations in conditions without trigger factors.
Se Ryung Yang,Min Hyung Kim,Na Mi Lee,Dae Yong Yi,Sin Weon Yun,Soo Ahn Chae,In Seok Lim,Eung Sang Choi 중앙대학교 의과대학 의과학연구소 2016 中央醫大誌 Vol.41 No.2
Purpose: A history of complex febrile seizure is associated with an increased risk to develop epilepsy. We examined the correlation between complex febrile seizures and duration of recognized fever prior to the onset of febrile seizure. Methods: This retrospective study included 680 children admitted to Chung-Ang University Hospital with febrile seizures between January, 2010 and December, 2014. Children were assigned to 4 groups based on the time of fever detection: Group 1 (at the time of seizure), Group 2 (<24 h prior to seizure), Group 3 (between 24 and 48 h prior to seizure), and Group 4 (>48 h prior to seizure). Results: A significant correlation was observed between the duration of recognized fever prior to the onset of febrile seizures and occurrence of complex febrile seizure (p = 0.005). Maximum temperatures before seizure and during seizure did not differ between the groups (p = 0.192 & p = 0.095, respectively). Complex febrile seizure was more common in Group 3 than in any other group. Additionally, on dividing the patients into those with fever duration <24 h and ≥24 h, incidence of complex febrile seizures in the latter group was higher. Incidence of complex febrile seizures in Group 3 was the highest among the groups even when the analysis was restricted t o patients having their first attack of febrile seizure. Conclusion: The duration of recognized fever prior to febrile seizures may be a risk factor for complex febrile seizures. Children having fever 24~48 hours prior to febrile seizure had a significantly higher incidence of complex febrile seizures.