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Ji‑Eun Ahn,Young‑Kyun Kim,Sang‑Hoon Yoon,Kee‑Ahn Lee 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.7
An equiatomic CoCrFeMnNi high entropy alloy (HEA) coating layer was prepared via a cold spray (CS) process. In orderto control the microstructure and nano-indentation properties of the CS HEA, heat treatments were employed. CS HEAcoating layer showed a heterogeneous microstructure where ultra-fine grains were formed at the particle interfaces, whilecoarse grains were formed inside the particles. Furthermore, deformation twins (DTs) were also formed inside the particlesdue to severe plastic deformation (SPD) in each particle generated during the CS deposition. For the 550 °C heat treatment(HT), fine Cr-rich precipitates were additionally formed at the grain boundary and particle boundary. By contrast, recrystallizationoccurred during 850 °C HT, while the size of the Cr-rich precipitate increased. The nano-indentation hardness ofthe CS HEA coating layer was 10.9 GPa, which was ~ 3 times higher than that of the conventional cast HEA. The superiorhardness of the CS HEA might has been enabled due to the combination of the high dislocation density, DTs, and ultra-finegrains. Based on the results above, the strategy to control the microstructure and mechanical properties through HT of theequiatomic CoCrFeMnNi HEA coating layer prepared via the CS process has been discussed.
Seong Hoon Kim,Ji Hoon Kim,Jae Hoon Lee,Dong‑Woo Suh,Jae Sang Lee 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.9
Prediction of retained austenite fraction is quite important in designing advanced high strength steels since retained austeniteis the source of transformation-induced plasticity. The present study investigates the phase constitution of a medium-carbonQ&P steel by comparing various approaches to the transformation stasis of bainitic ferrite and applying them to the partitioningprocess. Among them, the modified GEB approach gave the best agreement with the experimental observation, includingthe effects of heat-treatment condition and chemical composition on phase constitution. This indicates phase transformationduring partitioning can be effectively described by the physics of Gibbs energy balance approach.
Signed-DLMS 적응 알고리즘 이용한 무선 중계 간섭 제거기
유태훈(Tae-Hoon Yoo),우대호(Dae-Ho Woo),김주완(Dae-Ho Woo),하성희(Sung-Hee Ha),반지훈(Ji-Hun Van),이종현(Jong-Hyun Lee) 대한전자공학회 2007 대한전자공학회 학술대회 Vol.2007 No.7
In this paper, we study the signed- DLMS adaptive algorithm of wireless repeater for solving shadow region due to propagation between base station and mobile station. The the signed-DLMS algorithm reduces interference signals from multipath and solves the oscillation problem of repeater by estimation and cancellation. To efficiently reject interference signal. the signed-DLMS adaptive algorithm is applied. The computational complexities of the signed-DLMS are reduced verse standard LMS algorithm. Wireless ICS repeater based on signed-DLMS reduces the cost and is able to increase channel capacities.
( Sang-gyun Kim ),( Hyun-gon Kim ),( Seung-yup Lee ),( Hong-chul Lim ),( Ji-hoon Bae ) 대한슬관절학회 2018 대한슬관절학회지 Vol.30 No.3
Purpose: This study was conducted to investigate the outcomes of bearing exchange for the treatment of mobile bearing dislocation in medial unicompartmental knee arthroplasty (UKA). Materials and Methods: We retrospectively reviewed 18 patients (15 females and 3 males, mean age of 65 years) treated with bearing exchange following mobile bearing dislocation in medial UKA. The occurrence of bearing redislocation, the Oxford Knee Score, and radiographic changes at the last follow-up were investigated. Results: Bearing redislocation after bearing exchange occurred in 9 of 18 patients (50%). Of these 9 patients, 7 underwent conversion to total knee arthroplasty after bearing redislocation. The 9 patients without bearing redislocation showed good to excellent clinical outcomes at a mean followup of 55 months after bearing exchange. The non-redislocation group had a higher percentage of posterior dislocation of the bearing than the redislocation group (55.5% vs. 22.2%, p=0.040). Univariate logistic regression analysis showed no significant risk factors for bearing redislocation. Conclusions: This study showed a high rate of bearing redislocation after isolated, mobile bearing exchange for bearing dislocation following medial UKA. Therefore, bearing exchange as a sole treatment should be carefully considered in selected patients with correctable causes of bearing dislocation.
Outcomes of Therapeutic Modalities for Intractable Childhood Epilepsy
Hoon Chul Kang(강훈철),Ji Won Kwon(권지원),Yong Soon Hwang(황용순),Heung Dong Kim(김흥동),Sang Keun Park(박상근) 대한소아신경학회 2005 대한소아신경학회지 Vol.13 No.2
목 적 : 난치성 소아 간질 치료를 위해, 최근 개발된 항간질 약물, 프레드니솔론, 케톤생성식이요법, 간질수술, 미주신경자극술의 임상적 결과를 평가하였다. 방 법 : 1995년 7월부터 2003년 4월까지 상계백병원 간질센터에서 치료한 난치성 간질 환아 297명의 임상 결과를 후향적으로 분석하였다. 결 과 : 최근 개발된 항간질 약물이 투여된 290명 환아에서 20명(6.9%)에서만 추적 관찰기간 중 간질 완해물 유지하였다. 프레드니솔돈을 투여한 138명 환아에서 58명(42.0%)에서 약물 투여 중 간질 완해를 보였으나, 41명 환아에서 약물 중단 후 재발되었다. 케톤생성 식이요법은 162명에서 시도되어 74명(45.7%)에서 12개월 이상 식이요법을 유지하였으며, 간질 완해를 보인 37명(22.8%)을 포함하여 68명(42.0%)에서 50% 이상의 간질 횟수의 감소를 보였다. 간질 수술은 38명에서 시행되었으면 25명(65.8%)에서 Engel 구분 Ⅰ을 보였다. 미주신경자극술은 5명 환아에서 시행되어 2명에서만 50% 이상의 간질 횟수 감소를 보였다. 결 론 : 케톤생성 식이요법과 간질수술은 난치성 소아 간질 치료에 상당히 효과적인 치료였으나 프레드니솔론은 잦은 재발을 보였고 새로 개발된 항간질 약물은 난치성 간질의 완해를 유지함에 있어 한계가 있었다. Purpose : This study sought to evaluate the clinical outcomes of various therapeutic modalities, including newly-developed anti-epileptic drugs (AEDs), prednisolone, ketogenic diet (KD) epilepsy surgery, and vagus nerve stimulation (VNS), in treating intractable childhood epilepsy. Methods : Data of refractory epilepsy patients (n=297) treated from July 1995 through April 2003 at the epilepsy center of Sanggye Paik Hospital were retrospectively analyzed. Results : Newly-developed AEDs were primarily prescribed to 290 patients, although only 20 patients (6.9%) maintained a seizure- free state. Of 138 patients for whom prednisolone was prescribed, 58 patients (42.0%) showed complete seizure controls while 41 patients experienced relapse. KD was attempted and evaluated at 12 months in 162 patients, at which time 74 (45.7%) remained on the diet and 68 (42.0%) showed seizure reduction of greater than 50%, including 37 (22.8%) who were completely seizure free. Epilepsy surgery was undergone in 38 patients, and Engel class I was identified in 25 (65.8%) patients. VNS was administered to five patients, only two of whom obtained a seizure reduction of more than 50%. Result : Taken together, these findings suggest that considerable controls over intractable childhood epilepsy can be gained through KD and epilepsy surgery, whereas prednisolone treatment leads to somewhat more frequent relapses, and newly-developed AEDs are comparatively limited in their controls of refractory epilepsy.
Effects of Dexamethasone on Embryo Development and Hox Gene Expression Patterns in Mice
Sang Hoon Kim,Ji-Yeon Lee,Sung Joo Park,Myoung Hee Kim 대한의생명과학회 2011 Biomedical Science Letters Vol.17 No.3
During pregnancy, stress induces maternal glucocorticoid secretion, which in turn is known to affect structural malformation, retardation of growth, reduced birth weight of the fetus. As Hox genes are master transcription factors which fulfill critical roles in embryonic development, we aimed to explore the possibility that alterations of the Hox gene expression might be involved in stress-induced malformation. The pregnant mice were injected with dexamethasone at a dose of 1 mg/kg or 10 mg/kg on day 7.5, 8.5 and 9.5 p.c. (post coitum), as well as saline as control. Embryos of E11.5 and E18.5 were obtained by sacrificing pregnant animals. Weight and crown-rump length (CRL) were measured. RT-PCR was performed to examine the Hox gene expression levels. Embryos given dexamethasone at day 7.5~9.5 p.c. had small CRL and weighed less both in E11.5 and E18.5. The percentage of embryos showing abnormalities was high in groups received high dose of dexamethasone. To define the molecular basis for abnormal embryonic development, we analyzed the Hox gene expression pattern and found that many Hox genes display altered expression. Effects of prenatal dexamethasone treatment on embryonic development might be associated with the aberrant Hox gene expression.