Influence of heat‑treated Al-Si coating on the weldability and microstructural inhomogeneity for hot stamped steel resistance nut projection welds

Eun‑Joon Chun,Sung‑Sang Lim,Young‑Tae Kim,Ki‑Sung Nam,김영민,Young‑Whan Park,Siva Prasad Murugan,Yeong‑Do Park 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.1

Resistance nut projection weldability of Al–Si coated hot stamped steel (HSS) was investigated under the viewpoint of weldablecurrent range and joint strength (pull-out load). The microstructural inhomogeneities in the welds were also studied inorder to elucidate the factors affecting the joint strength of the welds. The weldability of the given Al–Si coated HSS wascompared with the weldability of an identical HSS without the Al–Si coating (Al–Si coating was polished out) and Zn coateddual phase steel. The weldable current range of Al–Si coated HSS was found to be narrower than that of the other materials. Furthermore, the average pull-out load within the weldable current range of the Al–Si coated HSS was the lowest among thethree materials. The reason for poor weld mechanical property of the Al–Si coated hot-stamped steel was attributed to themicrostructural inhomogeneities such as unmixed Al–Si coating layer at the edge of the nugget and the second phase Fe3(Al,Si) intermetallic compound. The formation of Fe3(Al, Si) phase was attributed to the solidification segregation of Al and Siduring the weld solidification and was confirmed with the numerical analysis of solidification segregation.

수지상세포의 방사선 저항성에 대한 연구

김은실,김종순,이명호,범희승,민정준,정환정,김성민,허영준,송호천,이제중 대한핵의학회 2003 핵의학 분자영상 Vol.37 No.3

목적 : 림프구와 비교되는 수지상 세포의 방사선 민감성을 보기 위하여 본 연구를 시행하였다. 대상 및 방법 : 말초혈액에서 분리한 T 림프구에 0 Gy, 10 Gy, 30 Gy의 방사선을 조사하고 4시간 후에 유세포 분석기를 이용하여 선량별 세포고사 빈도를 관찰하였다. 또한 조혈모세포에서 미성숙 및 성숙 수지상 세포를 단계적으로 분리 배양하여 각각 0 Gy, 10 Gy, 30 Gy, 100 Gy의 방사선을 조사하고 4시간, 24시간 그리고 48 시간 후에 선량별 세포고사 빈도를 관찰하였다. 사이토스핀(cytospin)슬라이드에 림프구와 미성숙 및 성숙 수지상세포를 3×104개 씩 분주하고 May Grunwald-Giemsa 염색한 후, 광학 현미경 하에서 각각의 세포군 당 100개의 세포에서 세포 면적당 핵의 면적 비를 측정하였다. 결과 : 림프구에서는 방사선조사 선량별로 세포고사 빈도가 유의하게 증가하였으나, 수지상 세포에서는 그 분화정도나 방사선조사 선량에 따른 세포고사의 빈도차이가 없었다. 또한 수지상 세포는 방사선선량과 관계없이 용량에 의존적으로 강력한 T-세포 자극능을 보였다. 림프구의 세포에 대한 핵의 면적 비는 미성숙 및 성숙 수지상세포의 세포에 대한 핵의 면적 비보다 현저히 큰 반면, 두 가지 수지상세포간에 유의한 차이는 없었다. 결론 : 수지상세포는 그 분화도와 상관없이 림프구에 비하여 방사선 저항성을 나타내었고, 이는 세포의 형태적 차이에 따른 표적의 크기와 관련이 있을 것으로 생각되며, 향후 분자 생물학적인 연구의 기초 자료로 활용할 수 있을 것으로 생각된다. Purpose : To evaluate radiation sensitivity of dendritic cells in comparison with lymphocytes. Materials and methods : T lymphocytes captured from peripheral blood were irradiated by 0 Gy, 10 Gy, 30Gy. Apoptosis was measured by flowcytometry for staining of Annexin V 4 hours after irradiation. Immature and mature dendritic cells processed from blood hematopoietic stern cell were irradiated by 0 Gy, 10 Gy, 30 Gy, 100 Gy respectively and apoptosis was measured by flowcytometry with time difference as 4h, 24h and 48h after irradiation. Morphometric analysis by percent nucleus was measured in three cell groups, also. Results : Lymphocytes showed radiation sensitivity by increasing apoptotic fraction according to radiation dose. However, both mature and immature dendritic cells showed consistent fraction of apoptosis in spite of increasing radiation dose. Percent nucleus ratio is significantly higher in lymphocytes than that of mature or immature dendritic cells. Stimulation of T-cell by dendritic cells was not changed after irradiation. Conclusion : Dendritic cells showed radioresistance which was associated with small size of nucleus in comparison with lymphocytes and this result would be used as a basal data of radio-labelling for the cellular trafficking studies in nuclear medicine fields.

다발성 간종괴의 형태로 나타난 특발성 과호산구 증후군 치험1예

최승오,연규민,이승민,김순제,왕준호,박형석,이재동,진춘조,이창훈,신현준,김정은 건국대학교 의과학연구소 2004 건국의과학학술지 Vol.14 No.-

Hypereosinophilic syndrome is characterized by persistent blood eosinophilia of 1,500/ul or more in the absence of known causes and multiorgan dysfunction by eosinophil-related tissue damage. In Korea, some cases of hypereosinophilic syndrome with hepatic involvement have been described with prolonged benign clinical courses. Most of them were diffuse or multifocal lesions in imaging studies, and a few case presenting as a single mass has been described. Here we report a case of hypereosinophilic syndrome with hepatic involvement in a 65-year-old man who presented with multifocal mass lesions. By abdominal US and CT scan, multiple, ill-defined nodules were detected in throughout the liver. Liver biopsy revealed severe eosinophilic hepatitis, suggestive of hypereosinophilic syndrome. Hepatic mass lesions improved after steroid administration for several weeks.

Successful Intubation using Angulated Video Laryngoscopy and a Back-up Head-elevated Position in a Patient with Diffuse Idiopathic Skeletal Hyperostosis: A Case Report

( Eun Hee Chun ),( Mi Hwa Chung ),( Eun Mi Choi ),( Jung Eun Kim ),( In-jung Jun ),( Jong Hee Park ),( Joon-sang Hyeon ),( Joo Hyun Jun ) 경희대학교 경희의료원 2020 慶熙醫學 Vol.35 No.1

Ligamentous ossification of the anterolateral spine is characteristic of diffuse idiopathic skeletal hyperostosis (DISH; i.e., ankylosing hyperostosis or Forestier’s disease). Cervical spine involvement can make airway management difficult during intubation. A patient with a history of impossible intubation resulting from the presence of large anterior cervical osteophytes presented for removal of the osteophytes. Preoperative diagnostic imaging revealed a larynx anteriorly displaced by osteophytes. The osteophytes were on the anterior surfaces of the third to seventh cervical vertebrae. Successful intubation was performed using an angulated curved video laryngoscope and a back-up head-elevated position (BUHE). The angulated curved video laryngoscope and BUHE position provided a good laryngeal view in a patient with DISH who had a larynx with osteophyte-associated anterior displacement. We suggest that these methods are an alternative for anesthesiologists during airway management of patients with difficult intubation.

Influence of Metallic Sodium on Repair Weldability for Type 316FR Stainless Steel

Eun-Joon Chun,Su-Jin Lee,Jeong Suh,Ju-Seung Lee,Namhyun Kang,Kazuyoshi Saida 대한용접·접합학회 2017 대한용접·접합학회지 Vol.35 No.1

The effect of residual metallic sodium on the solidification cracking susceptibility of type 316FR stainless steel was investigated via transverse-Varestraint tests. And a solidification brittle temperature range (BTR) of type 316FR stainless steel was 37 K. However, the BTR expanded from 37 to 67 K, as the amount of metallic sodium at the specimen surface increased from 0 to 7.99 mg/㎠. Microstructural observation of the weld metal suggested that metallic sodium existed in the weld metal, including in the cell boundaries, during welding solidification. Thermodynamic calculations suggested that sodium expanded the temperature range of solidliquid coexistence during welding solidification of the steel weld metal. Therefore, the increased solidification cracking susceptibility (i.e., expansion of the BTR) in the residual sodium environment was attributed to enhanced segregation of sodium during the welding solidification; this segregation, in turn, resulted in an expanded temperature range of solid-liquid coexistence.

Influence of Metallic Sodium on Repair Weldability for Type 316FR Stainless Steel

Chun, Eun-Joon,Lee, Su-Jin,Suh, Jeong,Lee, Ju-Seung,Kang, Namhyun,Saida, Kazuyoshi The Korean Welding and Joining Society 2017 대한용접·접합학회지 Vol.35 No.1

The effect of residual metallic sodium on the solidification cracking susceptibility of type 316FR stainless steel was investigated via transverse-Varestraint tests. And a solidification brittle temperature range (BTR) of type 316FR stainless steel was 37 K. However, the BTR expanded from 37 to 67 K, as the amount of metallic sodium at the specimen surface increased from 0 to $7.99mg/cm^2$. Microstructural observation of the weld metal suggested that metallic sodium existed in the weld metal, including in the cell boundaries, during welding solidification. Thermodynamic calculations suggested that sodium expanded the temperature range of solidliquid coexistence during welding solidification of the steel weld metal. Therefore, the increased solidification cracking susceptibility (i.e., expansion of the BTR) in the residual sodium environment was attributed to enhanced segregation of sodium during the welding solidification; this segregation, in turn, resulted in an expanded temperature range of solid-liquid coexistence.

A comparative study of pulp vitality following vital pulpotomy using calcium hydroxide-based sealants in beagle dogs

Gil Joon Jung, Se Eun Kim, Chun-Sik Bae, Kyung Mi Shim, Seok Hwa Choi, Seong Soo Kang1 충북대학교 동물의학연구소 2012 Journal of Biomedical and Translational Research Vol.13 No.4

Vital pulpotomy is a very useful method for disarming of canine tooth, tooth fracture, periodontitis, and malocclusion in veterinary dentistry. Calcium hydroxide is the material commonly used as a liner during vital pulpotomy. This creates a mineralized barrier by stimulating osteoblastic hard tissue repair, arrests the inflammatory response, and soothes dentin. However, the powder or mix type calcium hydroxide materials have many disadvantages due to complicated procedures for use and are hard to handle when vital pulpotomy is followed under general anesthesia in animals. This study was conducted in order to compare the effect of mix and premixed paste type calcium hydroxide as a liner in vital pulpotomy. Six beagle dogs underwent hemisection on the mesial root of the mandibular first molar and vital pulpotomy on the distal root of the first molar. On the distal root of the left and right mandibular first molar, mix type (DYCAL®, Dentsply, USA) and premixed paste type calcium hydroxide (VITAPEX®, Morita, Japan) were used as liners, respectively. Radiological evaluation was performed at immediate, 4, 12, and 20 weeks after vital pulpotomy. According to the results, all teeth had well-formed dentinal bridges, and there were no periradicular lucency, lamina dura loss, or anomalies of the pulp cavity. According to these results, on vital pulpotomy in animals, premixed paste type calcium hydroxide was easy to handle and decreased the anesthesia period due to a more convenient application procedure. A further study of many clinical cases is needed for evaluation of side effects and other problems.

980 MPa급 열연강의 권취온도와 탄화물 거동에 따른 신장플랜지성

천은준 ( Eun Joon Chun ),이주승 ( Ju Seung Lee ),도형협 ( Hyeong Hyeop Do ),김성주 ( Seong Ju Kim ),최윤석 ( Yoon Suk Choi ),박용호 ( Yong Ho Park ),강남현 ( Nam Hyun Kang ) 대한금속재료학회 ( 구 대한금속학회 ) 2012 대한금속·재료학회지 Vol.50 No.7

To analyze the factors on stretch-flangeability for 980 MPa-grade hot-rolled steels, two types of steels (Fe-Cr and Fe-Mo) were manufactured by hot-rolling. Manufactured steels at the low coiling temperature, such as 400 and 500℃, had poor stretch-flangeability due to un-uniformly distributed carbides and a large deviation of interphase hardness. However, when the coiling temperature was set at 650℃ with Fe-Cr steel, 998 MPa of ultimate tensile strength, 19% of total elongation and 65% of the hole expanding ratio were achieved by microstructural constituents of polygonal ferrite (PF) and granular ferrite (GF) dispersed with fine carbides (<50 nm). Therefore, the material to attain 980 MPa with superior formability was the Fe- Cr steel that was precipitation-hardened in polygonal ferrite and granular ferrite at the coiling temperature 650℃.

오스테나이트계 스테인리스강 레이저 용접부의 응고균열 거동 (Part 2)

천은준(Eun-Joon Chun),이수진(Su-Jin Lee),서정(Jeong Suh),강남현(Namhyun Kang),Kazuyoshi Saida 대한용접·접합학회 2016 대한용접·접합학회지 Vol.34 No.5

A numerical simulation of the solid/liquid coexistence temperature range, using solidification segregation model linked with the Kurz-Giovanola-Trivedi model, explained the mechanism of the BTR shrinkage (with an increase in welding speed) in type 310 stainless steel welds by reduction of the solid/liquid coexistence temperature range of the weld metal due to the inhibited solidification segregation of solute elements and promoted dendrite tip supercooling attributed to rapid solidification of laser beam welding. The reason why the BTR enlarged in type 316 series stainless welds could be clarified by the enhanced solidification segregation of impurity elements (S and P), corresponding to the decrement in δ-ferrite crystallization amount at the solidification completion stage in the laser welds. Furthermore, the greater increase in BTR with type 316-B steel was determined to be due to a larger decrease in δ-ferrite amount during welding solidification than with type 316-A steel. This, in turn, greatly increases the segregation of impurities, which is responsible for the greater temperature range of solid/liquid coexistence when using type 316-B steel.

다이오드 레이저 기반 자용성 합금 용사층 균질화 열처리에 따른 미세조직 변화

천은준(Eun-Joon Chun),서정(Jeong Suh),허선도(Sun-Do Huh) 대한용접·접합학회 2018 대한용접학회 특별강연 및 학술발표대회 개요집 Vol.2018 No.4