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S-709 Risk factors of renal involvement in patients with idiopathic inflammatory myopathies.
( Bong Woo Lee ),( Howook Jeon ),( Min Seok Choi ),( Jeniffer Lee ),( Sung-hwan Park ) 대한내과학회 2016 대한내과학회 추계학술대회 Vol.2016 No.1
Background: Renal involvement in patients with idiopathic inflammatory myopathies (IIM) is previously thought to be uncommon. However, recent studies reported that renal involvement may occur in nearly 20% of IIM patients, and some possible risk factors are proposed. Objectives: We investigate the prevalence, risk factors, and prognosis of renal involvement in Korean patients with IIM. Methods: Clinical and laboratory data of 50 patients diagnosed with IIM in Seoul St. Mary's hospital between 2005 and 2015 were investigated through retrospective medical chart review. AKI was defined as an acute doubling of serum creatinine level, and CKD as GFR less than 60 ml/min/1.73m2 over 3 months. And other renal involvement such as proteinuria more than 300mg/day or microscopic hematuria was evaluated Results: Eight patients were found to have renal involvement. The prevalence of renal involvement in our study population was similar to previous studies conducted in other countries (16% vs. 20%, respectively). However, clinical manifestations were different; there were no patients with AKI at initial diagnosis and no one progressed to CKD. All eight patients showed proteinuria or hematuria. When the potential risk factors (age at IIM onset, sex, type of IIM, underlying disease, serum muscle enzyme levels, presence of interstitial lung disease (ILD)) for renal involvement were analyzed, high level of serum muscle enzymes at the diagnosis was associated with renal involvement (CPK 5389 [2088-9662] vs. 1222 [177-3789] U/L, p=0.009; LDH 2323 [1084-2665] vs. 861.50 [633-1306] U/L, p=0.020). Neither the presence of interstitial lung disease nor the presence of other comorbities was related to renal involvement. The prognosis of the renal involvement was good; proteinuria or hematuria in six patients was abrogated with the use of steroid/immune suppressive agents. There was only 1 patient who had persistent proteinuria until she expired due to uncontrolled IIM. Conclusions: Renal involvement in patients with IIM is not rare in Korea and is associated with initial high level of serum muscle enzymes. The possibility of renal involvement should be considered and closely monitored when treating IIM patients.
Jung, Byung Te,Choi, HoWook,Park, Kyung Sun,Suh, Dong Hack 한국공업화학회 2003 Journal of Industrial and Engineering Chemistry Vol.9 No.2
The polyimidization of bis(trimethylsiIyl)urea with 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) in dimethylsulfoxide (DMSO) was carried out to produce a novel polyimide. New structure of polyimide was characterized by ¹H-NMR and FT-lR spectrum. The polymer has inherent viscosity of 0.385 dL/g and was stable up to at least 430℃ with 10% weight loss. A wide-angle X-ray diffractogram revealed that the polymer was semi-crystalline.
Thi Anh Nguyet Nguyen,Howook Choi,Moon-Jo Kim,Sung-Tae Hong,Heung Nam Han 한국정밀공학회 2022 International Journal of Precision Engineering and Vol.9 No.2
The athermal effect of electric current during electrically assisted (EA) annealing, which is a simple and cost-effective heat treatment technique, is assessed by comparing the performances of EA annealing and induction heat treatment (IHT), using aluminum alloy specimens with a high dislocation density from cold rolling. The dislocation densities after EA annealing and IHT are calculated using X-ray diffraction data to compare the performance of the processes. The performance of EA annealing clearly surpasses that of IHT in a certain temperature range. However, at higher temperatures, the thermal effect alone is able to induce nearly complete annihilation of dislocation density, thus, the practical advantage of EA annealing may diminish.
Electropulsing Treatment on Enhancement of Electrical Conductivity of Screen-Printed Ag Wire
Ju‑Won Park,Howook Choi,Hwangsun Kim,Simoon Sung,Hye‑Jin Jeong,Il Kim,Jaeseok Gong,Sung‑Tae Hong,Heung Nam Han 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.5
The effect of high electric current density on the sintering of Ag wires manufactured by screen printing is evaluated throughelectrical resistivity analysis and microstructure observation. Different forms (continuous and pulsed) of electric currentwith different current densities are applied to the specimens. Conventional heat treatment is also performed as a controlgroup to examine the athermal effect of electropulsing treatment. Compared to the conventional heat treatment, the resistivityis reduced more under the electropulsing treatment with continuous current for the same temperature and treatment time.Also, the process time of electropulsing treatment can be reduced by applying a pulse form of high density current insteadof continuous current without losing the benefit of enhanced reduction of resistivity. The microstructural observationsobtained from high angle annular dark field scanning transmission electron microscope and a digital precession instrumentclearly show that necking connecting the crystals is formed more firmly under electric current. In addition, the temperaturechange of Ag wire and substrate is calculated according to the change of the resistivity when the electric current is appliedto confirm the reliability.
Li, Yong-Fang,Hong, Sung-Tae,Choi, Howook,Han, Heung Nam Elsevier 2019 Materials characterization Vol.154 No.-
<P><B>Abstract</B></P> <P>Electrically assisted solid-state joining (or electrically assisted pressure joining, EAPJ) of dissimilar stainless steel 316L (SUS316L) and Inconel 718 (IN718) alloys is experimentally investigated. The specimen assembly for the experiment is comprised of two cylindrical solid specimens (SUS316L and IN718) with an identical geometry. In EAPJ, electric current and plastic compression are directly and simultaneously applied to the specimen assembly. The microstructural analysis confirms that crack/void-free joints are successfully fabricated by EAPJ in the selected dissimilar metal alloys without melting and solidification. An obvious atomic diffusion region at the joint interface is identified. The results of tensile tests show that all the joints fracture from the SUS316L side, which undergoes typical ductile fracture with large plastic deformation. The results of the present study confirm that the concept of EAPJ is applicable to solid state joining of dissimilar material combination.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Electrically assisted pressure joining of dissimilar metal alloys was conducted. </LI> <LI> Joining temperature was significantly lower than the melting temperatures. </LI> <LI> Solid state joint of stainless steel 316L and Inconel 718 alloys was fabricated. </LI> <LI> Tensile tests confirm the soundness of joints; no interfacial fracture occurred. </LI> </UL> </P>
Mounarik Mondal,Soumyabrata Basak,Hrishikesh Das,Sung-Tae Hong,Howook Choi,Ju-Won Park,Heung Nam Han 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.8 No.5
A bimetallic ring component is forged by a friction stir assisted forging (FS-forging). A cylindrical bimetallic blank, magnesium AZ31 cylinder (Mg core) tightly fitted inside an aluminum 6061-T6 tube (Al skin), is used. In the FS-forging, the frictional heat and stirring of rotating tool forge the blank into a desired shape, while simultaneously generate a solid-state joint between the Mg core and the Al skin, without additional external heating, as confirmed by the microstructural analysis and mechanical tests. The microstructural analysis also shows that the characteristics of the solid-state joint can be different depending on the process parameters.
탄소섬유 펼침 기술 및 이를 적용한 적층 복합재료의 기계적 특성
박성민 ( Sungmin Park ),김명순 ( Myungsoon Kim ),최윤성 ( Yoonsung Choi ),이은수 ( Eunsoo Lee ),유호욱 ( Howook Yoo ),천진성 ( Jinsung Chon ) 한국복합재료학회 2015 Composites research Vol.28 No.5
본 연구는 탄소섬유 펼침 기술을 이용한 적층 복합재료의 특성을 평가하였다. 섬유 펼침 기술이 적용되어 기존 12 K 탄소섬유 토우의 폭이 7 mm에서 20 mm로 늘어나면서 두께가 더 얇아졌다. 폴리프로필렌 필름을 spread tow에 함침시켜 프리프레그를 만들고 이를 적층 후 열압축 성형을 통해 시편을 제조하였으며 이들의 기공함유량 및 인장, 굴곡 시험을 통해 물리적, 기계적 물성을 평가하였다. 그 결과, 탄소섬유 펼침 기술이 적용된 적층 복합재료의 기공함유량이 기존의 섬유 토우를 사용한 것보다 작게 나타났고, 섬유함유량이 낮았음에도 불구하고 기계적 물성이 향상됨을 알 수 있었다. This paper reports a study on a method for achieving lightweight thermoplastic laminate composites referred to as tow spreading technology. Thickness of an unspread 12 K carbon fiber tow is reduced by increasing the tow width from 7 mm to 20 mm. The polypropylene (PP) film was used to stabilize and impregnate the spread tow, covering it into a partially consolidated prepreg: 12 K carbon fiber spread tow/PP. Laminates were fabricated from the spread tow prepreg and control laminate composites were produced from unspread tow prepreg consisting of 12 K carbon fiber and PP. The void content, tensile and flexural properties of the composite laminates were investigated. Consequently, the spread tow laminate composite exhibited lower void content and improved mechanical properties.