• Proceedings of the Korean Vacuum Society Conference
• /
• 한국진공학회 2009년도 제38회 동계학술대회 초록집
• /
• pp.232-232
• /
• 2010

정보화 산업의 발달은 DRAM, flash memory 등을 포함한 기존의 반도체 메모리 소자를 대체할 수 있는 차세대 메모리 소자에 대한 개발을 요구하고 있다. 특히 magnetic random access memory (MRAM)는 SRAM과 대등한 고속화 그리고 DRAM 보다 높은 기록 밀도가 가능하고 낮은 동작 전압과 소비전력 때문에 대표적인 차세대 비휘발성 메모리로 주목받고 있다. 또한 MRAM소자의 고집적화를 위해서 우수한 프로파일을 갖고 재증착이 없는 나노미터 크기의 magnetic tunnel junction (MTJ) stack의 건식 식각에 대한 연구가 선행되어야 한다. 본 연구에서는 고밀도 반응성 이온 식각법(Inductively coupled plasma reactive ion etching; ICPRIE)을 이용하여 재증착이 없이 우수한 식각 profile을 갖는 CoFeB과 IrMn 박막을 형성하고자 하였다. Photoresist(PR) 및 Ti 박막의 두 가지 마스크를 이용하여 HBr/Ar, HBr/$O_2$/Ar 식각 가스들의 농도를 변화시키면서 CoFeB과 IrMn 박막의 식각 특성들이 조사되었다. 자성 박막과 동일한 조건에 대하여 hard mask로서 Ti가 식각되었다. 좋은 조건을 얻기 위해 HBr/Ar 식각 가스를 이용 식각할 때 pressure, bias voltage, rf power를 변화시켰고 식각조건에서 Ti 하드마스크에 대한 자성 박막들의 selectivity를 조사하고 식각 profile을 관찰하였다. 식각 속도를 구하기 위해 alpha step(Tencor P-1)이 사용되었고 또한 field emission scanning electron microscopy(FESEM)를 이용하여 식각 profile을 관찰함으로써 최적의 식각 가스와 식각 조건을 찾고자 하였다.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 1998년도 추계 학술대회논문집
• /
• pp.121-126
• /
• 1998

A numerical optimization procedure is developed to find the inlet velocity profile that yields the most uniform epitaxial layer in a vertical MOCVD reactor. It involves the solution of fully elliptic equations of motion, temperature, and concentration; the finite volume method based on SIMPLE algorithm has been adopted to solve the Navier-Stokes equations. The overall optimization process is highly nonlinear and has been efficiently treated by the sequential linear programming technique that breaks the non-linear problem into a series of linear ones. The optimal profile approximated by a 6th-degree Chebyshev polynomial is very successful in reducing the spatial non-uniformity of the growth rate. The optimization is particularly effective to the high Reynolds number flow. It is also found that a properly constructed inlet velocity profile can suppress the buoyancy driven secondary flow and improve the growth-rate uniformity.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 한국소음진동공학회 2003년도 추계학술대회논문집
• /
• pp.418-423
• /
• 2003

The balancing performance of an automatic ball balancer (ABB) in the vertical or horizontal position is studied in this paper. Considering the effects of gravity and angular velocity profiles, a physical model for an ABB installed on the Jeffcott rotor is adopted. The non-linear equations of motion for the rotor with ABB are derived by using Lagrange's equation. Based on derived equations, dynamic responses for the rotor are computed by using the generalized-u method. From the computed responses, the effects of gravity and angular velocity profiles on the balancing performance are investigated. It is found that the rotor with ABB can be balanced regardless of the gravity effect. It is also shown that a smooth velocity profile yields relatively smaller vibration amplitude than a non-smooth velocity profile.

• The Transactions of the Korean Institute of Electrical Engineers A
• /
• 제49권11호
• /
• pp.531-535
• /
• 2000

A method to compute the reactive powers of the added buses by the decoupled UPFC model for the optimal voltage profile is presented, by which the voltage magnitudes of PQ buses can get closer to the reference value(usually one p.u.). The performance index for assessing how much the voltage magnitude is closer to the reference value is defined as the squared sum of the present voltage minus the reference voltage multiplied by the weighting number associated with the relative importance of the buses. Numerical example in a 10-unit 39-bus power system with 2 UPFC's shows that the performance index can be very much reduced by operating many UPFC's with the reactive powers for the optimal voltage profile proposed in this paper.

• IE interfaces
• /
• 제13권4호
• /
• pp.703-708
• /
• 2000

In manufacturing processes, manufacturing features always deviate somewhat from their nominal design specifications due to several types of errors. This study suggests a fitting algorithm of the geometric profile parameters of leading and trailing edges for turbine compressor airfoils. In reality, industry personnels inspect the airfoil profile by trial-and-error method to determine the geometric feature parameters. In this study we propose an exploration approach based on factorial design with center point to minimize the effect of measurement errors caused by probe slip. By adopting the fitting method developed in this paper, one can enhance the precision and efficiency of fitting the airfoil edge profile.

• Proceedings of the Korea Information Processing Society Conference
• /
• 한국정보처리학회 2011년도 춘계학술발표대회
• /
• pp.1108-1111
• /
• 2011

최근 E-러닝 발전과 함께 U-러닝에 대한 관심이 집중되고 있으며 이와 관련된 다양한 관련 표준들이 채택되고 있다. 기존의 E-러닝 관련 기술들이 웹에 기반한 학습을 지향하였다면 U-러닝에서는 다양한 환경에서 학습자가 학습의 맥락을 이어가며 학습을 하는 것으로서 언제, 어디서나, 누구나 학습을 진행하여 생활의 학습화를 지원할 기술을 필요로 한다. 즉, U-러닝에서는 다양한 사용 환경에서 학습이 이루어지므로 사용 환경에 적합한 학습이 이루어져야 하고, 이를 위해 사용 환경 맞춤형 콘텐츠 적응화 기술이 필요하다. 크게 사용 환경 맞춤형 콘텐츠 적응화 기술은 다양한 단말기 정보를 포함한 사용 환경 정보를 표현할 수 있는 기술과 사용자의 사용 환경 정보를 분석하는 기술, 사용 환경에 적합한 콘텐츠를 구성하는 기술로 구성된다. 이에 본 연구에서는 지식서비스 USN 산업원천 기술개발 과제의 세부과제인 'U-러닝 환경 표준 및 표준 명세 개발 및 검증' 과제에서 콘텐츠 적응화를 위해 연구 개발된 사용 환경 정보를 표현하는 U-러닝 프로파일에 대하여 소개한다.

• Proceedings of the KSRS Conference
• /
• 대한원격탐사학회 2004년도 Proceedings of ISRS 2004
• /
• pp.83-86
• /
• 2004

With the proliferation of smart devices, applications under ubiquitous environment must provide transparent access to computer resources. However, existing u-Logistics systems can not properly react on such requirements, because the status information of objects is input only in fixed milestones by system's operators. In this paper, we introduce an event notification service suitable for u-Logistics environment. The system is based on RFID infrastructure and provides real-time tracking by combining the event of objects with location information received from GPS satellites. The system also provides a graphical user interface based on a state/transition approach, making it easy that clients facilitate definition of profile, and uses XML structure to more easily represent and exchange events.

• Proceedings of the Optical Society of Korea Conference
• /
• 한국광학회 2006년도 동계학술발표회 논문집
• /
• pp.111-112
• /
• 2006

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 한국소성가공학회 2002년도 춘계학술대회 논문집
• /
• pp.48-53
• /
• 2002

Sheet or plate bending is one of the most important industrial metal forming processes. And considerable attention has been focused on gaining a better understanding of many of bending characteristics. One of defaults in bending process is the springback. In this study, the springback characteristics of tailor-welded strips in U-bending process was investigated. Furthermore, not only the relationships between the springback and the process variables such as the geometry of the tools and thickness combination of workpiece but also the heat effect which affects the springback due to welding process was experimentally considered. First, tailor-welded strips are joined by the laser welding process and consisted of two types of thickness combinations of the SCPI sheet, 0.8t${\times}$1.2t and 0.8${\times}$1.6t to investigate the effect of different thickness combination on the springback. Secondly, two different directionally welded strips, one was welded along the centerline of the strip-width and the other was along the centerline of strip-length, were adopted to compare the effects of the location of weld line on the springback. And three punch profile radii of 3, 9, and 15 m were used. Some cases of the experimental results were simulated by using a commercial FEM code, PAM-STAMP to compare the experimental results to the analytical ones.

• Journal of the Society of Naval Architects of Korea
• /
• 제50권4호
• /
• pp.206-216
• /
• 2013

The present study considers the prediction of wind-induced heel of cruise ship and its stabilization. Wind load in ocean exerts on the surface of superstructure of cruise ship, which causes the heel moment on the ship. The calculation of wind load starts from choosing wind speed profile, so that the logarithmic wind profile model is applied in this study. Heel moment by wind load is calculated by adopting approximate formulation and applied to the ship motion analysis in time domain. Motion stabilizers, such as stabilizing fin and U-tube tank, are considered to reduce the heel effect as well as excessive roll motion. From this study, it is expected that the present method can be applied to the prediction and stabilization of the heel motion of cruise ships.