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김광석,최돈현,정승부,Kim, Kwang-Seok,Choi, Don-Hyun,Jung, Seung-Boo 한국마이크로전자및패키징학회 2014 마이크로전자 및 패키징학회지 Vol.21 No.2
Technology for high power devices has made impressive progress in increasing the current density of power semiconductor, system module, and design optimization, which realize high power systems with heterogeneous functional integration. Depending on the performance development of high power semiconductor, packaging technology of high power device is urgently required for efficiency improvement of the device. Power device packaging must provide superior thermal management due to high operating temperature of power modules. Here we, therefore, review critical challenges of typical power electronics packaging today including core assembly processes, component materials, and reliability evaluation regulations.
김광석,Hye-Min Lee,Ju-Hwan Kim,Injun Jung,나원진,이병선,Byung-Joo Kim,김정필 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.112 No.-
Despite active research on supercapacitors to address the demand for high-power backup power systems,the energy storage performance of supercapacitors at high current densities has scope for improvementowing to the poor kinetics of active materials. In this study, multiscale porous carbon-based active materialswere designed to improve the kinetics and power density of supercapacitors. These materials werefabricated by spinodal decomposition of a mixture comprising an epoxy resin, a curing agent, and a porogen,to which graphene was added to optimize the carbonaceous microstructure. The resultant materialexhibited a wider pore-size distribution and considerably improved microstructure than commercialactivated carbon (YP-50F). The charge-transfer resistance of the sample containing 3 wt.% graphene(A-EM3) was considerably lower than that of YP-50F owing to the microstructural improvement. Furthermore, the effective ionic conductivity of A-EM3 was approximately three times higher than thatof YP-50F owing to enhanced mass transfer. A-EM3 exhibited a high specific capacitance (81.0 F g1) atthe highest current density (10.0 A g1). Thus, spinodal decomposition and graphene addition are effectivemeans to fabricate high-power-density supercapacitors.
김광석,오동근,여지숙,Kim, Kwang-Seok,Oh, Dong-Geun,Yeo, Ji-Suk 한국도서관정보학회 2012 한국도서관정보학회지 Vol.43 No.1
이 연구는 2011년 현재 운영중인 7개 외국학술지지원센터의 운영효과를 점검하기 위해 그 비용과 편익을 분석하였다. 사업개시부터 30년 경과시점을 기준으로 한 투자타당성 분석 결과, 비용편익 비율(BCR)은 0.99, 내부수익률(IRR)은 5.49%, 누적순현재가치(NPV)는 -507백만원으로 나타났다. 다만 민감도분석에서는 저널 이용건수와 사회적 할인율, 중복구독 중단 등의 항목의 변화에 따라 비용편익비율이 변화할 수 있음을 제시하였다. This article analyzes the costs and benefits of the seven individuals centers of Foreign Research Information Center. Results of the investment feasibility analysis based on 30 years time span show that 0.99 of BCR (Benefit-Cost Ratio), 5.49% of IRR (Internal Rate of Return), and -507 million Won of NPV (Net Present Value). Sensibility analysis suggests that BCR can be influenced by the journal usage, social rate of discount, and elimination of the duplicate journal among individual centers.
잉크젯 프린팅 방식으로 형성된 구리 배선의 전기적 특성 평가
김광석,구자명,정재우,김병성,정승부,Kim, Kwang-Seok,Koo, Ja-Myeong,Joung, Jae-Woo,Kim, Byung-Sung,Jung, Seung-Boo 한국마이크로전자및패키징학회 2010 마이크로전자 및 패키징학회지 Vol.17 No.3
직접인쇄기술 방식은 기존의 포토리소그래피 방법을 이용한 패터닝 기술에 비해 저비용, 간단한 공정 과정, 친환경성 등 여러 장점들로 인해 미세 회로 형성 분야의 그린 테크놀로지로 최근 각광받고 있다. 이러한 프린팅 기반의 전자기술을 상용화하기 위해서는 프린팅 방식으로 형성된 회로의 전기적 특성 평가가 필수적인데, 이에 본 연구에서는 구리 잉크를 이용하여 잉크젯 프린팅 방식으로 2 가지 타입, parallel transmission line(PTL)과 coplanar waveguide(CPW) 구조의 회로를 형성하고 $250^{\circ}C$에서 30분 동안 소결하여 완성하였다. 전류-전압 그래프로 직류 저항을 측정하여 벌크 구리의 비저항 값의 약 3.3배되는 평균 0.558 ${\mu}{\Omega}{\cdot}cm$의 비저항 값을 도출하였고 회로의 고주파 특성 평가를 위해 주파수 범위 0~30 GHz에서 probe station chuck과 샘플 간의 갭 유무에 따른 scattering parameter를 측정하였다. 모든 시편에서 5 dB 이하의 반사 특성을 보였으며, PTL 회로가 CPW 구조보다 전반적으로 더 좋은 통과 특성을 나타내었다. Direct printing technology is an attractive metallization method, which has become immerging as "Green technology" to the conventional photolithography, on account of low cost, simple process and environment-friendliness. In order to commercialize the printed electronics in industry, it is essential to evaluate the electrical properties of conductive circuits using direct printing technology. In this contribution, we focused on the electrical characteristics of inkjet-printed circuits. A Cu nanoink was inkjet-printed onto a Bisaleimide triazine(BT) substrate with parallel transmission line(PTL) and coplanar waveguide(CPW) type, then was sintered at $250^{\circ}C$ for 30 min. We calculated the resistivity of printed circuits through direct current resistance by the measurement of I-V curve: the resistivity was approximately 0.558 ${\mu}{\Omega}{\cdot}cm$ which is about 3.3 times that of bulk Cu. Cascade's probe system in the frequency range from 0 to 30 GHz were employed to measure the Scattering parameter(S-parameter) with or without a gap between the substrate and the probe station chuck. The result of measured S-parameter showed that all printed circuits had over 5 dB of return loss in the entire frequency range. In the curve of insertion loss, $S_{21}$, showed that the PTL type circuits had better transmission of radio frequency (RF) than CPW type.
구치부(臼齒部) 도재전장주조관(陶在前裝鑄造冠) 변연형태(邊緣形態)에 따른 응력분석(應力分析)
김광석,송광엽,박찬운,Kim, Kwang-Seok,Song, Kwang-Yup,Park, Charn-Woon 대한치과보철학회 1987 대한치과보철학회지 Vol.25 No.1
To study the mechanical behaviors of the margins of porcelain-fused-to-metal crown on the posterior teeth, 5 types of margins on the lower first molar were chosen, and then the finite element models were constructed. 50kg forces were applied to the porcelain on the axial wall supported by the metal vertically. The displacements and stresses of the porcelain-fused-to-metal crown were analyzed to investigate the influence of the type of margins. The results were as follows; 1. High tensile stresses were exhibited on the porcelain of the portion of the coronal line angle insufficient metallic support. 2. In case metal coping had a good supporting form to vertical force, uniform compressive stresses were exhibited on their supporting form. 3. Tensile stresses in the inframetallic margin on the series of the shoulder with a bevel margins were decreased in the bevel portion. 4. Principal stresses on the metal of the chamfer marginal portion were decreased comparing with the series of the shoulder margins. 5. The noticeable compressive stress gradients were exhibited between axial cement layer and metal on the series of the shoulder margins. 6. The principal stresses on the marginal cement layer were higher than that of the occlusal surface and axial wall.