Fatigue Behavior of High-Mn Steels

Sangshik Kim(김상식) 대한기계학회 2019 대한기계학회 춘추학술대회 Vol.2019 No.5

S-N fatigue behavior of anodized 7050-T7451 produced in different electrolytes

Sangshik Kim 한국표면공학회 2013 한국표면공학회 학술발표회 초록집 Vol.2013 No.11

Structural and Electrical Properties of ZrO₂ Films Coated onto PET for High-Energy-Density Capacitors

Sangshik Park 한국진공학회(ASCT) 2014 Applied Science and Convergence Technology Vol.23 No.2

Flexible ZrO₂ films as dielectric materials for high-energy-density capacitors were deposited on polyethylene terephthalate (PET) substrates by RF magnetron sputtering. The growth behavior, microstructure and electrical properties of the flexible ZrO₂ films were dependent on the sputtering pressure and gas ratio. Although ZrO₂ films were deposited at room temperature, all films showed a tetragonal crystalline structure regardless of the sputtering variables. The surface of the film became a surface with large white particles upon an increase in the O₂/Ar gas ratio. The RMS roughness and crystallite size of the ZrO₂ films increased with an increase in the sputtering pressure. The electrical properties of the ZrO₂ films were affected by the microstructure and roughness. The ZrO₂ films exhibited a dielectric constant of 21∼38 at 1 kHz and a leakage current density of 10<SUP>-6</SUP>∼10<SUP>-5 </SUP>A/cm² at 300 kV/cm.

Electrical Properties of Ba(Ti<SUB>1-x</SUB>,Mg<SUB>x</SUB>)O₃ Films Prepared by E-Beam Evaporation

Sangshik Park,Jaeho HA 한국표면공학회 2008 한국표면공학회 학술발표회 초록집 Vol.2008 No.-

금융분야 클라우드 컴퓨팅 적용모델 및 보안기술 연구

민상식(Sangshik Min),성재모(Jaemo Seung) 한국정보보호학회 2011 情報保護學會誌 Vol.21 No.8

최근 금융권에서는 서버의 가용성 향상, 관리의 편의성, 운영비용의 절감 등을 위하여 가상화 기술을 기반으로 한 프라이빗 클라우드 컴퓨팅 환경의 도입이 시작 되고 있다. 하지만 퍼블릭 클라우드 서비스를 이용하기 위해서는 전자금융사고에 대비한 보안기술, 법·제도에 대한 정비, 금융 서비스를 위한 SLA(Service Level Agreement)등이 고려되어야 하므로 많은 어려움이 있다. 본 논문에서는 컴퓨팅 환경의 미래가 될 클라우드 컴퓨팅 기술이 전자금융서비스에서 이용될 수 있는 방법에 대해 살펴보고 적용 가능한 보안방안을 제시하여 향후 클라우드 컴퓨팅 기반 전자금융서비스의 안전성 강화를 위한 연구에 기반이 되고자 한다.

Structural and Electrical Properties of ZrO₂ Films Coated onto PET for High-Energy-Density Capacitors

Park, Sangshik The Korean Vacuum Society 2014 Applied Science and Convergence Technology Vol.23 No.2

Flexible $ZrO_2$ films as dielectric materials for high-energy-density capacitors were deposited on polyethylene terephthalate (PET) substrates by RF magnetron sputtering. The growth behavior, microstructure and electrical properties of the flexible $ZrO_2$ films were dependent on the sputtering pressure and gas ratio. Although $ZrO_2$ films were deposited at room temperature, all films showed a tetragonal crystalline structure regardless of the sputtering variables. The surface of the film became a surface with large white particles upon an increase in the $O_2/Ar$ gas ratio. The RMS roughness and crystallite size of the $ZrO_2$ films increased with an increase in the sputtering pressure. The electrical properties of the $ZrO_2$ films were affected by the microstructure and roughness. The $ZrO_2$ films exhibited a dielectric constant of 21~38 at 1 kHz and a leakage current density of $10^{-6}{\sim}10^{-5}A/cm^2$ at 300 kV/cm.

Fatigue crack formation and growth from localized corrosion in Al–Zn–Mg–Cu

Kim, Sangshik,Burns, James T.,Gangloff, Richard P. Elsevier 2009 Engineering fracture mechanics Vol.76 No.5

<P><B>Abstract</B></P><P>The effect of precorrosion on the fatigue life of aluminum alloy 7075-T6511 was measured, physical characteristics of corrosion topography plus fatigue damage were established by microscopy, and a corrosion modified equivalent initial flaw size (CM-EIFS) was established using fracture mechanics modeling. Fatigue life is reduced by clustered corrosion pits on the L–S surface from laboratory-EXCO exposure. Cracks initiate from pits clustered as a semi-elliptical surface micronotch rather than the deepest pits, consistent with shape-dependent stress intensity. Marker band analysis establishes that the number of cycles to form a crack about a pit cluster can be a significant fraction of total fatigue life. The CM-EIFS, back-calculated from fracture mechanics analysis of measured fatigue life, equals measured initiating-pit cluster size provided that important inputs are provided; such favorable comparison validates this approach to corrosion-fatigue interaction. Calculated CM-EIFS provides a metric to characterize alloy corrosion damage, and can be used to forward-model the effects of stress and loading environment on fatigue life distribution, critical for efficient alloy development. Use in prognosis of the fatigue performance of a service-corroded surface is hindered by uncertain non-destructive characterization of corrosion topography.</P>

Landau Diamagnetism in Disordered Mesoscopic Systems

OH,Sangshik 濟州大學校 基礎科學硏究所 1994 基礎科學硏究 Vol.7 No.1

We evaluate the disorder-averaged magnetic susceptibility expressed in the linear response formulation and get the well-known result that it is same as the Landau diamagnetic susceptibility of a clean system. For isolated mesoscopic systems, we consider the zero-mode diamagnetic fluctuation arising from the long-range correlation of magnetic currents in real space and show that it can be up to (??/h) times larger than its average value.

O2O(Online to Offline) 서비스 디자인을 활용한 반디앤루니스 서점에 대한 사례연구

이상식(Sangshik Lee) 한국산업정보학회 2017 한국산업정보학회논문지 Vol.22 No.1

본 연구는 온·오프라인의 경쟁이 치열한 출판물 유통환경에서 차별화된 서비스 개념으로 운영되고 있는 반디앤루니스 센텀시티점에 대한 사례 연구이다. 반디앤루니스는 국내에 14개의 오프라인 서점과 온라인 서점을 갖고 있는 대형서점 중 하나이다. 본 연구의 목적은 반디앤루니스의 O2O 서비스와 서비스 디자인에 대한 독특한 시례와 관행을 통해서 시사점을 제공하는데 있다. 반디앤루니스의 역사, 서비스 컨셉, 가치, 성과 등을 다양한 매체를 활용해 찾고, O2O서비스와 서비스 디자인에 대한 기존 연구들을 살펴 보았다. 즐거운 고객 경험을 제공하기 위해서는 고객의 관점에서 서비스를 디자인해야 하며, 고객이 오랫동안 머물 수 있도록 고객의 라이프 스타일을 고려한 다양한 서비스를 제공할 수 있어야 한다. 빅데이터, 사물인터넷, 인공지능(AI)의 시대에 온·오프라인의 경계를 허물고 고객 경험을 향상시킬 수 있는 서비스를 제공하기 위해서는 정보·통신기술을 활용한 서비스 디자인 혁신이 필요할 것이다. This Study Focuses on the Customer Experience Story of Bandi&Luni’s Centum City branch which Offers the Different Service Concept on the Competitive Book Selling Market. Bandi&Luni’s Stands as one of the Largest Bookstore Chains that has 14 Offline Bookstores and an Online Bookstore Shop. The Purpose of this Study takes Lessons from the Unique Practices and Efforts of Bandi&Lunis’s Online-to-Offline(O2O) Service and Service Design. In Order to Achieve this Propose, we Investigated the History, Service Concept, Value, and Performance of Bandi&Luni’s from a Variety of sources and Reviewed the Previous Literatures of O2O Service and Service Design. In order to Offer Better Customer Experience the Service should be Designed from Customer’s View and be Delivered through the Lifecycle of Customers. In a era of Big Data, IOT(internet of things), AI(artificial intelligence), The Service Design Innovation using Information and Communication Technology will be needed in order to Break down the Boundaries Between Online and Offline.

Effects of Sputtering Pressure on the Properties of BaTiO₃ Films for High Energy Density Capacitors

Park, Sangshik Materials Research Society of Korea 2014 한국재료학회지 Vol.24 No.4

Flexible $BaTiO_3$ films as dielectric materials for high energy density capacitors were deposited on polyethylene terephthalate (PET) substrates by r.f. magnetron sputtering. The growth behavior, microstructure and electrical properties of the flexible $BaTiO_3$ films were dependent on the sputtering pressure during sputtering. The RMS roughness and crystallite size of the $BaTiO_3$ increased with increasing sputtering pressure. All $BaTiO_3$ films had an amorphous structure, regardless of the sputtering pressures, due to the low PET substrate temperature. The composition of films showed an atomic ratio (Ba:Ti:O) of 0.9:1.1:3. The electrical properties of the $BaTiO_3$ films were affected by the microstructure and roughness. The $BaTiO_3$ films prepared at 100 mTorr exhibited a dielectric constant of ~80 at 1 kHz and a leakage current of $10^{-8}A$ at 400 kV/cm. Also, films showed polarization of $8{\mu}C/cm^2$ at 100 kV/cm and remnant polarization ($P_r$) of $2{\mu}C/cm^2$. This suggests that sputter deposited flexible $BaTiO_3$ films are a promising dielectric that can be used in high energy density capacitors owing to their high dielectric constant, low leakage current and stable preparation by sputtering.