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Compact Coarse Approach Mechanism for a Scanning Probe Microscope
Kyongjun Kim,Yongho Seo,Duhwan Hwang,Junhong Kim 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.2
We report a compact design for a coarse approach mechanism, the so-called `walker', for a low-temperature ultra-high-vacuum scanning probe microscope. We adapted the slip-stick principle with three actuators driven by the time sequential scheme suggested by Pan {\it et al.} The shear piezo-stack was replaced by three rectangular pieces of a piezoelectric (PZT) actuator to reduce the walker volume. Three slip-stick actuators were used rather than six actuators in the original design. By using polished sapphire and rough alumina plates, we implemented perfect sticking and a sliding interface. Our design minimizes usage of glue or epoxy, where attachment strength would be deteriorated by repeated temperature cycling. By using teflon material, we reduced the frictional force of sliding parts. Without a metallic spring, elastic motion was provided by the teflon material against the holding force. A moving velocity of 18 μm/s and a step distance of 0.3 μm were measured at room temperature. We report a compact design for a coarse approach mechanism, the so-called `walker', for a low-temperature ultra-high-vacuum scanning probe microscope. We adapted the slip-stick principle with three actuators driven by the time sequential scheme suggested by Pan {\it et al.} The shear piezo-stack was replaced by three rectangular pieces of a piezoelectric (PZT) actuator to reduce the walker volume. Three slip-stick actuators were used rather than six actuators in the original design. By using polished sapphire and rough alumina plates, we implemented perfect sticking and a sliding interface. Our design minimizes usage of glue or epoxy, where attachment strength would be deteriorated by repeated temperature cycling. By using teflon material, we reduced the frictional force of sliding parts. Without a metallic spring, elastic motion was provided by the teflon material against the holding force. A moving velocity of 18 μm/s and a step distance of 0.3 μm were measured at room temperature.
Functional-power-aware Partial Gating Method for Low Power Scan-shift
Kyongjun Noh,Tae Hee Lee,Jun-Dong Cho 대한전자공학회 2018 Journal of semiconductor technology and science Vol.18 No.1
This paper presents a new scheme to minimize scan-shift power for test reliability with minimized functional power overhead, which is achieved by selective insertion of signal gating-logic considering the loading condition and switching activity of scan shift signals. The proposed methodology also considers practical design issues such as logic-timing overhead and cell-congestion impact associated with scan-shift power reduction. In experimental results with industrial system-on-chip (SoC) designs, the proposed power-aware gating-logic-insertion methodology not only achieved reduction of scan-shift power but also improved functional power up to 10% compared with the conventional full-scan gating scheme.
이경준(Kyongjun Lee),양경수(Kyung-Soo Yang),윤동혁(Dong-Hyeog Yoon) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
Flow-induced forces on two identical nearby circular cylinders immersed in the cross flow at Re =100 were numerically studied. We consider all possible arrangements of the two circular cylinders in terms of the distance between the two cylinders and the inclination angle with respect to the direction of the main flow. It turns out that significant changes in the characteristics of flow-induced forces are noticed depending on how the two circular cylinders are positioned, resulting in quantitative changes of force coefficients on both cylinders. Collecting all the numerical results obtained, we propose a contour diagram for drag coefficient and lift coefficient for each of the two cylinders. The perfect geometrical symmetry implied in the flow configuration allows one to use those diagrams to estimate flow-induced forces on two identical circular cylinders arbitrarily positioned in physical space with respect to the main flow direction.
두 개의 원형 실린더를 지나는 유동의 레이놀즈 수 효과
이경준(Kyongjun Lee),양경수(Kyung-Soo Yang),최춘범(Choon-Bum Choi) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10
As a follow-up of our previous studies on flow-induced forces on two identical nearby circular cylinders immersed in the cross flow at Re=100(1) and flow patterns past them(2), we present Reynolds-number effects on the forces and patterns by further computing flows with Re=40, 50, 160. We consider all possible arrangements of the two circular cylinders in terms of the distance between the two cylinders and the angle inclined with respect to the main flow direction. Collecting all the numerical results obtained, we propose contour diagrams for mean force coefficients and their rms of fluctuation as well as for flow patterns and Strouhal number for each Re. These diagrams shed light on a comprehensive picture on how the wake interaction between the two cylinders alters depending on Re.As a follow-up of our previous studies on flow-induced forces on two identical nearby circular cylinders immersed in the cross flow at Re=100 and flow patterns past them, we present Reynolds-number effects on the forces and patterns by further computing flows with Re=40, 50, 160. We consider all possible arrangements of the two circular cylinders in terms of the distance between the two cylinders and the angle inclined with respect to the main flow direction. Collecting all the numerical results obtained, we propose contour diagrams for mean force coefficients and their rms of fluctuation as well as for flow patterns and Strouhal number for each Re. These diagrams shed light on a comprehensive picture on how the wake interaction between the two cylinders alters depending on Re.