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PAN계 탄소섬유의 제조 및 탄화 조건에 따른 특성 분석
이현재,원종성,임성찬,이태상,윤준영,이승구,Lee, Hyun Jae,Won, Jong Sung,Lim, Sung Chan,Lee, Tae Sang,Yoon, Jun Young,Lee, Seung Goo 한국섬유공학회 2016 한국섬유공학회지 Vol.53 No.2
In this study, PAN (polyacrylonitrile)-based carbon fiber was prepared under different carbonization conditions. Carbonization of oxi-PAN fiber was performed under four different temperature conditions. Changes in the characteristics of these carbon fibers prepared under each condition were studied using various analyses. Crystalline characteristics of carbon fiber such as crystallinity and crystal size were analyzed using X-ray diffraction (XRD) and Scherrer's equation, based on the XRD patterns, respectively. The tensile strength and modulus of these carbon fibers were measured through a tensile test. Thermal characteristics were analyzed using a thermogravimetric analyzer (TGA). The result showed that the crystal size and crystallinity of the carbon fibers increased with carbonization temperature. Furthermore, both mechanical strength and thermal resistance were also observed to improve with carbonization temperature. Finally, a relationship between carbonization temperature, thermal properties, and mechanical properties of the carbon fibers was derived.
S-Hippuryl Thioglycolyl Glycine : A New Chromogenic Substrate for Dipeptidyl Carboxypeptidases
이현재,Lee Hyun-Jae Korean Chemical Society 1975 대한화학회지 Vol.19 No.4
Dideptidyl carboxypeptidases와 angiotenisn-coverting enzyme의 새로운 기질불질로서 thiol ester 인 S-Hippuryl thioglycolyl glycine을 합성하였으며, 이 기질에 의한 간편하고도 예민한 효소 활성도의 정량방법을 제시하였다. 이 경우 효소반응 생성물인 thioglycolyl glycine은 반응계중에 첨가한 5,5-dithio-bis-(2-nitrobenzoic acid), DTNB와 쉽게 반응하여 410nm에서 강한 흡광스펙트럼을 갖는 5-thio-2-nitrobenzoic acid(${\varepsilon}M=1.36{\times}10^4$)을 형성함으로서 효소의 새로운 미량정량 방법으로 이용 가치가 크다고 본다. A spectrophotometric assay technique is descriead for the measurement of free SH-groups in the enzyme reaction mixture. The method utilizes a new substrate, S-hippuryl-thioglycolyl-glycine(S-Hip-thioglycol-Gly) which is the basis for a convenient assay of angiotensin-converting enzyme and other dipeptidyl carboxypeptidases. This substrate contains an appropriately located thioester linkage that is hydrolyzed by the converting enzyme and other dipeptidyl carboxypeptidases. One of the products, thioglycolyl glycine, is readily measured by reaction with Ellman's reagent, 5,5'-dithio-bis-(2-nitrobenzoic acid), DTNB, to produce 5-thio-2-nitrobenzoic acid which has a strong absorption band at 410 nm. The method is sensitive (${\varepsilon}M = 1.36{\times}10^4$ at 412 nm) and can be applied as a continuous recording with DTNB present in the enzymatic reaction mixture.
석회석을 원료로 사용한 재생용지의 친환경 In-situ Filler로서의 광학적 특성 연구
이현재,이로운,김춘식,남성영,서영범,안지환,Lee, Hyun-Jae,Lee, Lown,Kim, Chun-Sik,Nam, Seong-Young,Seo, Yung-Bum,Ahn, Ji-Whan 한국세라믹학회 2014 한국세라믹학회지 Vol.51 No.2
The study was performed with low-grade limestone, which is used to make cement or is disposed of due to its low CaO content. In this study, the optimal condition of limestone with which to manufacture precipitated calcium carbonate (PCC) and limestone in fiber was determined through in-situ reactions. The best firing condition is with slaked lime with rapid cooling after 2 h of firing at $1000^{\circ}C$. In addition, the content of CaO can be increased by sorting the low-grade limestone using a 200 mesh filter, and the optical quality of old newspaper (ONP) was similar when using both low-grade and high-grade limestone. Also, controlling the particle size of PCC is an important factor pertaining to the optical characteristics of paper.
이중 반응기 조건 및 비균일계 조건에서의 초음파 에너지 및 화학적 효과 평가
이현재,손영규,Lee, Hyeon Jae,Son, Younggyu 한국지하수토양환경학회 2017 지하수토양환경 Vol.22 No.5
The effects of ultrasound in heterogeneous system were investigated in three kinds of ultrasonic systems including a bath-type system (System #1), a double-bath-type system (System #2), and a double-bath-type system partly filled with glass beads (System #3). The ultrasound energy and its attenuation were quantified using calorimetry and the sound pressure measurement method. The sonochemical effects mainly involved in radical oxidation reactions were quantified using KI dosimetry. It was found that ultrasound energy was significantly attenuated in System #2 and #3 due to the presence of solid materials such as a submerged stainless steel reactor and glass beads. However, in spite of low ultrasound energy status, sonochemical oxidation reactions occurred more violently due to the presence of glass beads in System #3. In addition, calorimetry was more adequate to estimate the total energy status of ultrasound in sonoreactors compared to the sound pressure measurement method.
이현재,함세영,박삼규,이충모,오윤영,웨이밍량,Lee, Hyun-Jae,Hamm, Se-Yeong,Park, Samgyu,Lee, Chung-Mo,Oh, Yun-Yeong,Liang, Wei Ming 대한자원환경지질학회 2015 자원환경지질 Vol.48 No.4
지질학적, 물리탐사기법, 지질공학적 방법을 통하여 함안군 도항리 6호고분의 축조 형태, 고분 축조에 사용된 재료의 원산지와 공학적 성질, 봉분과 석실부에 대한 안정성 등을 고찰하였다. 고분의 기반암인 함안층은 풍화를 받아 인력으로 굴착이 용이한 암반 특성을 나타내었다. 전기비저항 탐사에 의하면 봉분은 토사부를 나타내는 저비저항대와 암석편의 함량이 많은 암석부의 고비저항대로 구분되었다. 대부분의 석실부 개석은 함안층과 동일한 암석으로 구성되어 있으나, 개석의 일부는 연구지역의 최남단에서 산출되는 흑운모화강암과 동일하다. 토질 시험에 의하면, 봉분의 토사부는 낮은 함수비, 낮은 간극비, 적정한 단위중량으로 보아 다짐 정도가 매우 높은 재료임을 지시한다. 또한 봉분의 암석부의 강도는 일반적인 암반의 전단강도를 초과하고 있어 매우 안정성 있게 유지되고 있는 것으로 해석된다. Hamangun Dohangri $6^{th}$ tumulus was characterized by using geological, geophysical, and geotechnical surveys in terms of the shape of the tombs, origin and geotechnical properties of tomb materials, safety of grave mound and burial chamber. The bedrock (Haman Formation sedimentary rock) forming the ground of the tomb, is weathered such that men can excavate the ground. The mound tomb is classified into soil part and rock part by low resistivity and high resistivity, respectively, through electrical resistivity survey. The burial chamber is mostly made by Haman Formation while some part is composed of granitic rock that is distributed in the most southern district of the study area. According to soil tests, the soil part of mound tomb shows low water content, low pore ratio, and proper unit weight that indicate highly compacted material. Additionally, the mound tomb is safe because the strength of the rock part of the mound tomb exceeds that of general rock.
조선수리업종 석면노출 근로자들의 흉부방사선상 석면관련 폐질환 소견의 발생양상
이현재,홍영습,손지언,이영일,김상훈,임형준,김정만,김준연,Lee Hyun Jae,Hong Young Seoub,Son Ji Eun,Lee Young Ill,Kim Sang Hoon,Im Hyoung June,Kim Jung Man,Kim Joon Youn 한국생명과학회 2006 생명과학회지 Vol.16 No.1
모 조선수리업에 근무하는 1,086명 중 석면에 노출되는 작업공정에 10년 이상 근무한 근로자 118명을 대상으로 단면조사연구를 수행하였다. 연구대상자들에 대해 흥부방사선검사, 폐기능검사와 미국의 산업안전보건청 석면표준, 의학적 감시 프로그램(OSHA asbestos standard, medical surveillance program)에 따라 국내 실정에 맞게 일부 편집한 설문조사를 시행하였고 아울러 이들의 작업장에 대한 작업환경측정 자료도 분석하였다. 흉부방사선검사상 석면관련 폐질환 소견의 유병율은 118명의 근로자중 16명으로 $13.6\%$였다. 흉부방사선검사상 정상군에 비해 석면관련 폐질환 유소견군에서 유의한 요인들은 폐기능검사상 이상소견, 기침, 가래, 호흡기 질환의 과거력, 근무력이었다. 본 연구 결과를 통해 볼 때 폐기능검사 소견상 이상소견, 기침과 가래의 임상증상을 호소하거나 호흡기질환의 과거력, 20년 이상의 근무력이 있는 근로자에 대해서는 석면관련 폐질환의 엄격한 관리가 필요할 것으로 생각된다. 그리고, 본 연구에서 관련성 여부를 완전히 배제할 수 없었던 요인들에 대해서는 향후 광범위한 전향적 연구를 통하여 연관성을 규명하여 석면노출 사업장의 의학적 감시 프로그램에 적극 활용되기를 기대한다. There was cross-sectional study on investigating the factors related asbestos-related disease on chest radiograph of workers exposed to asbestos in ship repair. According to Occupational Safety & Health Administration asbestos standard, medical surveillance, chest radiologic study, pulmonary function test and medical questionnaire are performed in 118 subjects exposed to asbestos for 10 years or more in ship repair. The sixteen out of 118 subjects $(13.6\%)$ were observed asbestos-related disease finding on chest radiography. Significant factors related to those finding on chest radiography were abnormal pulmonary function test, cough, sputum, past history of respiratory disease, work duration. Workers with Significant factors related asbestos-related disease finding on chest radiography should be managed on a strict program. Further, factors unrelated with asbestos-related disease finding on this study should be evaluated prospectively for medical surveillance program of workers exposed to asbestos.
이현재,Lee, Hyeon-Jae 한국자연공원협회 1989 한국자연공원 Vol.43 No.-
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