800 MPa급 고강도강 용접금속의 미세조직 특성 비교 연구

이재희,김상훈,윤병현,김환태,길상철,이창희,Lee, Jae-Hee,Kim, Sang-Hoon,Yoon, Byung-Hyun,Kim, Hwan-Tae,Kil, Sang-Cheol,Lee, Chang-Hee 대한용접접합학회 2011 대한용접·접합학회지 Vol.29 No.1

Microstructural characteristics of two high strength (600 MPa & 800 MPa) weld metals produced by flux-cored arc welding process (FCAW) were evaluated. The 600 MPa grade weld metal was consisted of 75% acicular ferrite and 25% ferrite which was formed at relatively high temperature (grain boundary ferrite, widmanstatten ferrite, polygonal ferrite). However, the 800 MPa grade weld metal was composed of about 85% acicular ferrite and 15% low temperature forming phases (bainite, martensite). The prior austenite grain size of 800 MPa grade weld metal was decreased by solute drag force. The compositions and sizes of inclusions which are the dominant factors for the formation of acicular ferrite were analyzed by a transmission electron microscopy (TEM). In both 600 MPa and 800MPa grade weld metals, the inclusions were mainly consisted of Ti-oxide and Mn-oxide, and the average size of inclusions was $0.7{\mu}m$. The 800 MPa grade weld metal exhibited higher tensile strength and similar toughness compared with the 600 MPa grade weld metal. This result is mainly due to a higher fraction of low temperature products and a lower fraction of grain boundary ferrite in the 800 MPa grade weld metal.

소아 폐질환에서 폐생검의 유용성

이재희,이소연,김자형,김봉성,홍수종,Lee, Jae Hee,Lee, So Yeon,Kim, Ja Hyung,Kim, Bong Sung,Hong, Soo-Jong 대한소아청소년과학회 2003 Clinical and Experimental Pediatrics (CEP) Vol.46 No.12

Purpose : The aim of this study is to evaluate the value of lung biopsies for the management of children with lung disease. Methods : We retrospectively reviewed 19 lung biopsies done at Asan Medical Center, Seoul between 1993 and 2001. Data gathered included demographic information, underlying conditions, diagnosis before biopsy, final diagnosis, change in therapy, morbidity and mortality. Results : Nineteen patients underwent lung biopsy. Among them, 13 patients were male and six patients were female; the median age was 3.6 years(0.8 to 8.6 years). Twelve patients underwent open lung biopsies and seven patients had thoracoscopic biopsies. The overall diagnosis rate was 95 %. The most common diagnosis was interstitial lung disease(12 patients, 64%) and infection was detected in four patients(21%). The biopsy-proven bronchiolitis obliterance was confirmed in two of seven patients suspected by CT findings. Specific treatment was changed after biopsy in 16 patients (85%). The morbidity & overall mortality rates of the patients were 5%(one patient) and 21%(four patients) respectively. Only one complication was seen : empyema. The causes of death were acute respiratory distress syndrome(one patient), respiratory failure(two patients), and septicemia(one patient). Conclusion : The lung biopsy is a safe procedure and it contributes to more accurate diagnosis and proper management of pediatric lung diseases. We recommend lung biopsies should be considered more positively in the diagnosis of pediatric lung diseases.

보철물(補綴物) 장착시(裝着時) 치근막(齒根膜)과 치조골(齒槽骨)의 변화(變化)에 관(關)한 X선학적(線學的) 연구(硏究)

이재희,Lee, Jae-Hee 대한치과보철학회 1969 대한치과보철학회지 Vol.9 No.1

Intra-oral films of 155 patients were taken on the areas of Gold Crown-Bridges, S. P. Bridges and Partial Dentures. And the author observed periodontal ligaments widening rates, the presence of periapical lesions and the alveolar bone patterns on the Partial Denture Saddle portions. The results were as follows : 1. Periodontal ligaments a) Periodontal ligaments widening rate increased obviously with the duration of wearing those prosthetic appliances. b) Periodontal ligaments widening rate was the highest in partial denture wearing patients, and then that of S. P. Crown Bridge patients, Gold Crown Bridge wearing females, Gold Crown Bridge males were the sequences. 2. Periapical lesions a) Periapical lesions increased with the wearing duration of those prosthetic appliances. But they did not increase in proportion to the duration. Periapical lesions were about the same in the teeth with those appliances showing relatively higher rate in Partial Denture abutment teeth and the lowest in Gold-Bridge abutment teeth. 3. Alveolar bone of Partial Denture saddle portion One third of all(32%) were normal with their smooth and compact bone pattern so that they were considered to perform normal function.

불화수소산 음독에 의한 심정지 1례

이재희,정진희,어은경,Lee, Jae-Hee,Jung, Jin-Hee,Eo, Eun-Kyung 대한임상독성학회 2007 대한임상독성학회지 Vol.5 No.2

Hydrofluoric acid is a weak inorganic acid used for etching and as rust removals. Systemic toxicity after oral ingestion induces rapid development of hypocalcemia and hyperkalemia, leading to ventricular fibrillation and finally asystole. We report a case of intentional ingestion of hydrofluoric acid producing an altered mental state at the time of the patient's arrival in the emergency department. The patient died approximately 80 minutes after the exposure with asystol.

Liquid Liquid Extraction-GC/MS에 의한 항산화제(BHA, BHT) 및 살충제(Fenvalerate, Allethrin)의 동시분석

이재희,배준현,강준길,김연두,Lee, Jae-Hee,Bae, Jun-Hyun,Kang, Jun-Gill,Kim, Youn-Doo 대한화학회 2003 대한화학회지 Vol.47 No.6

LLE-GC/MS법을 사용하여 내분비계 교란물질로 추정되는 항 산화제 및 살충제를 동시에 분석할 수 있는 방법을 고안하였다. 본 연구에서 사용한 항 산화제는 butylated hydroxy anisole(BHA) 및 butylated hydroxy toluene (BHT)이고, 살충제는 allethrin 및 fenvalerate이었다. 표준시료에 대한 분석결과에서 검출한계(LOD)는 0.071~0.159 ng/ml이었으며, 이 때 상대표준편차는(%RSD)는 1.41~5.34이었다. 한강, 금강, 낙동강 및 섬진강 수계 중에서 이들 화합물들은 검출되지 않았다. 합성한 시료의 경우, 검출한계(LOD)는 0.051~0.132 ng/ml이었으며, 이 때 상대표준편차(%RSD)는 6.39~13.4% 이었다.

Solid Phase Microextraction-GC/MS에 의한 플라스틱가소제(DMP, DEP, DBP, BBP, DEHP, DnOP)의 동시분석

이재희,배준현,강준길,김연두,Lee, Jae-Hee,Bae, Jun-Hyun,Kang, Jun-Gill,Kim, Youn-Doo 대한화학회 2004 대한화학회지 Vol.48 No.1

SPME-GC/MS법을 사용하여 내분비계 교란물질로 추정되는 플라스틱 가소제류를 동시에 분석할 수 있는 방법을 고안하였다. 본 연구에서 사용한 플라스틱 가소제는 dimethyl phthalate(DMP), diethyl phthalate(DEP), dibutyl phthalate(DBP), benzylbutyl phthalate(BBP), diethylhexyl phthalate(DEHP), di-n-octyl phthalate(DnOP)이었다. 표준 시료에 대한 분석결과에서 검출한계(LOD)는 0.163~0.299 ng/ml, 상대표준편차는(%RSD)는 5.85~15.80이었다. 본 방법을 사용하여 한강, 금강, 낙동강 및 섬진강에서 채취한 시료를 분석한 결과, DBP와 DEHP 만이 4대강 모두에서 미량 검출되었으며, DBP와 DEHP의 농도는 각각 0.192~1.270 ng/ml 및 0.077~1.102 ng/ml 범위를 보였다.

유리침투 알루미나 복합체의 물성에 미치는 유리조성의 영향 (II) : La₂O₃의 영향

이재희,김철영,Lee, Jae-Hee,Kim, Cheol-Young 한국세라믹학회 2004 한국세라믹학회지 Vol.41 No.12

[ $SiO_2-B_{2}O_3-Al_{2}O_3-CaO-La_{2}O_3$ ]계 유리에서 $La_{2}O_3$를 변화시키며 다양한 조성의 유리를 만든 후 이를 다공성 알루미나에 침투시켜 알루미나-유리 복합체를 얻었다. 여기서 유리의 조성 변화에 따른 침투특성 및 기계적 강도의 변화를 관찰하였다. 유리중의 $La_{2}O_3$는 유리의 고온 점도를 감소시켜 유리의 젖음성과 유동성을 향상시키고 유리의 침투를 용이하게 한다. 유리가 다공성 알루미나에 침투하여 기공을 메우면서 일부 알루미나를 용해시킨다. 이 유리 용융물 중 $Al_{2}O_3$ 성분은 결정질 알루미나에 다시 석출하여 입자성장이 일어나는데 이때 특정 방향으로 알루미나 입자가 성장한다. $La_{2}O_3$가 20 몰 $\%$ 첨가된 유리를 침투시켰을 때 유리가 결정화하여 복합체의 강도를 증진시켰다. Glasses of $SiO_2-B_{2}O_3-Al_{2}O_3-CaO-La_{2}O_3$ with various amounts of $La_{2}O_3$ were infiltrated into a porous alumina to make an alumina-glass composite. The infiltration characterization and bending strength of the composite were examined in terms of glass composition. $La_{2}O_3$ in the glass decreased the high temperature viscosity and this enhanced the wetting behaviour of this glass to alumina, and made glass infiltration easier. The infiltrated glass dissolved the alumina skeleton, and $Al_{2}O_3$ component in the glass melt reprecipitated on the alumina. The grain growth occurred to a specific crystal direction. The glass containing $20mole\%$ of $La_{2}O_3$ was crystallized after infiltration, and this enhanced the bending strength of the composite.

제대군인의 재취업 및 창업 활성화 방안에 대한 연구

이재희,하규수,김홍,Lee, Jae-Hee,Ha, Kyu-Soo,Kim, Hong 한국벤처창업학회 2007 벤처창업연구 Vol.2 No.1

영관 및 위관급 제대군인 중 군인연금을 받지 못하거나 연금 수령액이 적은 장기복무 제대군인에 대해 양극과 해소차원에서 우선적으로 일자리가 마련되도록 맞춤식 직업교육 기회를 부여하고 사회에서 요구하는 능력개발에 가용조직력과 역량을 집중하는 한편, 중기복무자에 대한 직업훈련과 일자리 확보, 의무복무자에 대한 지원방안도 적극 추진해나가야 할 것이다. 범국가적인 지원 시스템과 지원 정책의 마련을 위한 정책을 제시하면 다음과 같다. 첫째, 정부부처 내 관련기관간의 업무를 분담 조정해야한다. 둘째, 범정부적 차원의 제대군인 일자리 창출이 이루어져야한다. 셋째, 전역 예정자에 대한 Pre-Retirement 프로그램 개발과 예산지원이 이루어져야한다. 넷째, 범국가적 차원에서 취업지원이 이루어져야한다. 다섯째, 인턴십 제도의 이용으로 취업의 기회를 확대해야 한다. 여섯째, 취업기관 간 공조체제가 이루어져야한다.

마이크로파 조사가 산화그래핀의 화학적 박리에 미치는 효과

이재희,황기완,정영훈,김의태,Lee, Jae-Hee,Hwang, Ki-Wan,Jeong, Young-Hoon,Kim, Eui-Tae 한국재료학회 2013 한국재료학회지 Vol.23 No.12

Graphene oxide has been synthesized by microwave-assisted exfoliation of graphite oxide prepared by modified Hummers method. Graphite was oxidized in a solution of $H_2O_2$ and $KMnO_4$ at $65{\sim}80^{\circ}C$, followed by 10 % $H_2O_2$ solution treatment at $80{\sim}90^{\circ}C$. The graphite oxide was exfoliated under microwave irradiation of 1 kW and was reduced to graphene effectively by hydrazine hydrate ($H_4N_2{\cdot}H_2O$) treatment. The exfoliation of graphene oxide was significantly affected by the microwave irradiation on (heating)/off (cooling) period. An on/off period of 10 s/20 s resulted in much more effective exfoliation than that of 5 s/10 s with the same total treatment time of 10 min. This can be explained by the higher exfoliation temperature of 10 s/20 s. Repetition of the graphite oxidation and exfoliation processes also enhanced the exfoliation of graphene oxide. The thickness of the final graphene products was estimated to be several layers. The D band peaks of the Raman spectra of the final graphene products were quite low, suggesting a high crystal quality.

CO₂ 레이저 열분해법을 이용한 실리콘 나노입자 합성 시 H₂ 유량이 나노입자 특성에 미치는 영향

이재희,김성범,김종복,황택성,이정철,Lee, Jae Hee,Kim, Seongbeom,Kim, Jongbok,Hwang, Taekseong,Lee, Jeong Chul 한국재료학회 2013 한국재료학회지 Vol.23 No.5

Silicon nanoparticle is a promising material for electronic devices, photovoltaics, and biological applications. Here, we synthesize silicon nanoparticles via $CO_2$ laser pyrolysis and study the hydrogen flow effects on the characteristics of silicon nanoparticles using high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and UV-Vis-NIR spectrophotometry. In $CO_2$ laser pyrolysis, used to synthesize the silicon nanoparticles, the wavelength of the $CO_2$ laser matches the absorption cross section of silane. Silane absorbs the $CO_2$ laser energy at a wavelength of $10.6{\mu}m$. Therefore, the laser excites silane, dissociating it to Si radical. Finally, nucleation and growth of the Si radicals generates various silicon nanoparticle. In addition, researchers can introduce hydrogen gas into silane to control the characteristics of silicon nanoparticles. Changing the hydrogen flow rate affects the nanoparticle size and crystallinity of silicon nanoparticles. Specifically, a high hydrogen flow rate produces small silicon nanoparticles and induces low crystallinity. We attribute these characteristics to the low density of the Si precursor, high hydrogen passivation probability on the surface of the silicon nanoparticles, and low reaction temperature during the synthesis.