• Title/Summary/Keyword: Rotation Mode

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CHARACTERIZATION OF MAGNETIZATION BEHAVIOR IN Co/Pd PERPENDICULAR ANISOTROPIC MULTILAYERS

  • Oh, Hoon-Sang;Joo, Seung-Ki
    • Journal of the Korean Magnetics Society
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    • v.5 no.5
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    • pp.655-658
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    • 1995
  • Magnetization behavior of sputter-deposited Co/Pd multilayers were characterized, and it has been found that even when the multilayers are sputtered at low pressure (10 mTorr), the coercivity of the multilayers can be increased to large extent without noticeable change of saturation magnetization by increasing the deposition pressure of Pd underlayer. It turned out that the surface topology of Pd underlayer gets rough as deposition pressure increases, which consequently affects the magnetization reversal mode of Co/Pd multilayers from domain wall motion to magnetic spin rotation. The enhancement of coercivity is attributed to the domain wall pinning effect which is comected with the surface roughness of Pd underlayer on which Co/Pd multilayers grow.

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Performance Evaluation of A Tunable Dispersion Compensator based on Strain-Chirped Fiber Bragg Grating in a 40 Gb/s Transmission Link

  • Kim, Chul-Han;Bae, Jun-Key;Lee, Kwan-Il;Lee, Sang-Bae
    • Journal of the Optical Society of Korea
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    • v.12 no.4
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    • pp.244-248
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    • 2008
  • We have evaluated the performance of strain-chirped fiber Bragg grating (FBG) based tunable dispersion compensator in a 40 Gb/s transmission link. In our proposed compensator, the value of dispersion could be changed from -353 ps/nm to -962 ps/nm by adjusting the rotation angle of the metal beam on which the FBG was mounted. In order to evaluate the effect of ripples in reflectivity and variations in passband of the FBG based dispersion compensator, transmission performance has been measured with our tunable dispersion compensator. Error-free transmission of a 40 Gb/s non-return-to-zero (NRZ) signal over conventional single-mode fiber (SMF) was achieved.

Fast Response Technique 2 Quadrant DC Motor Speed Control

  • W. Piyarat;V. Tipsuwanporn;W. Sawangsinkasikit;Lee, M. lajindarairerk;P. Thepsatorn
    • 제어로봇시스템학회:학술대회논문집
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    • 1999.10a
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    • pp.244-247
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    • 1999
  • This paper presents a methodology of the technique for controlling DC motor drive by implementation of 2-quadrant operating mode which can ensure the torque controlling and speed with response time less than 2 seconds at all loading conditions. By implementation of BRM technique, energy is fed with definite values of BRM 256 bits, with different patterns of high accuracy, and fixing scan time at 0.667 ms, the ripple is less than 1%, thus high efficiency can be achieved, from the consequence of the accuracy of energy feeding at low current. The stability of the whole system can be determined from circle criterion by root locus method . The instant reverse direction of rotation can be done by decreasing the energy to the lowest level while motor is running with no load and variable load at the speed about 100-120 rpm and 50-60 rpm.

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Analysis of Acquisition Parameters That Caused Artifacts in Four-dimensional (4D) CT Images of Targets Undergoing Regular Motion (표적이 규칙적으로 움직일 때 생기는 4DCT 영상의 모션 아티팩트(Motion Artifact) 관련된 원인분석)

  • Sheen, Heesoon;Han, Youngyih;Shin, Eunhyuk
    • Progress in Medical Physics
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    • v.24 no.4
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    • pp.243-252
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    • 2013
  • The aim of this study was to clarify the impacts of acquisition parameters on artifacts in four-dimensional computed tomography (4D CT) images, such as the partial volume effect (PVE), partial projection effect (PPE), and mis-matching of initial motion phases between adjacent beds (MMimph) in cine mode scanning. A thoracic phantom and two cylindrical phantoms (2 cm diameter and heights of 0.5 cm for No.1 and 10 cm for No.2) were scanned using 4D CT. For the thoracic phantom, acquisition was started automatically in the first scan with 5 sec and 8 sec of gantry rotation, thereby allowing a different phase at the initial projection of each bed. In the second scan, the initial projection at each bed was manually synchronized with the inhalation phase to minimize the MMimph. The third scan was intentionally un-synchronized with the inhalation phase. In the cylindrical phantom scan, one bed (2 cm) and three beds (6 cm) were used for 2 and 6 sec motion periods. Measured target volume to true volume ratios (MsTrueV) were computed. The relationships among MMimph, MsTrueV, and velocity were investigated. In the thoracic phantom, shorter gantry rotation provided more precise volume and was highly correlated with velocity when MMimph was minimal. MMimph reduced the correlation. For moving cylinder No. 1, MsTrueV was correlated with velocity, but the larger MMimph for 2 sec of motion removed the correlation. The volume of No. 2 was similar to the static volume due to the small PVE, PPE, and MMimph. Smaller target velocity and faster gantry rotation resulted in a more accurate volume description. The MMimph was the main parameter weakening the correlation between MsTrueV and velocity. Without reducing the MMimph, controlling target velocity and gantry rotation will not guarantee accurate image presentation given current 4D CT technology.

A STUDY ON THE GENERATION OF EO STANDARD IMAGE PRODUCTS: SPOT

  • JUNG HYUNG-SUP;KANG MYUNG-HO;LEE YONG-WOONG;LEE HO-NAM;WON JOONG-SUN
    • Proceedings of the KSRS Conference
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    • 2004.10a
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    • pp.216-219
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    • 2004
  • In this study, the concept and techniques to generate the level lA, lB and 2A image products have been reviewed. In particular, radiometric and geometric corrections and bands registration used to generate level lA, lB and 2A products have been focused in this study. Radiometric correction is performed to take into account radiometric gain and offset calculated by compensating the detector response non-uniformity. And, in order to compensate satellite altitude, attitude, skew effects, earth rotation and earth curvature, some geometric parameters for geometric corrections are computed and applied. Bands registration process using the matching function between a geometry, which is called 'reference geometry', and another one which is corresponds to the image to be registered is applied to images in case of multi-spectral imaging mode. In order to generate level-lA image products, a simple radiometric processing is applied to a level-0 image. Level-lB image has the same radiometry correction as a level-lA image, but is also issued from some geometric corrections in order to compensate skew effects, Earth rotation effects and spectral misregistration. Level-2A image is generated using some geo-referencing parameters computed by ephemeris data, orbit attitudes and sensor angles. Level lA image is tested by visual analysis. The difference between distances calculated level 1 B image and distances of real coordinate is tested. Level 2A image is tested Using checking points.

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DEEP-South: The Photometric Study of Non-Principal Axis Rotator (5247) Krylov

  • Lee, Hee-Jae;Moon, Hong-Kyu;Kim, Myung-Jin;Kim, Chun-Hwey;Durech, Josef;Park, Jintae;Roh, Dong-Goo;Choi, Young-Jun;Yim, Hong-Suh;Oh, Young-Seok
    • The Bulletin of The Korean Astronomical Society
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    • v.41 no.2
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    • pp.49.2-49.2
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    • 2016
  • The number of discovery of asteroids with peculiar rotational states has recently increased, and hence a novel approach for lightcurve analysis is considered to be critical. In order to investigate objects such as Non-Principal Axis (NPA) rotator, we selected a NPA candidate, (5247) Kryolv as our target considering its Principal Axis Rotation (PAR) code and the visibility in early 2016. The observations of Krylov were made using Korea Microlensing Telescope Network (KMTNet) 1.6 m telescopes installed at the three southern sites with TO (Target of Opportunity) observation mode. We conducted R-band time-series photometry over a total of 51 nights from January to April 2016 with several exposures during each allocated run. The ensemble normalization photometry was employed using the AAVSO Photomtric All-Sky Survey (APASS) catalog for the standardization. We successfully confirmed its NPA spin state based on the deviation from the reduced lightcurve, and thus Krylov is recorded as the first NPA rotator of its kind in the main-belt, with its precession and rotation periods, $P{\varphi}=81.18h$ and $P_{\Psi}=67.17h$, respectively. In this paper, we present the spin direction, the 3D shape model and taxonomy of the newly confirmed NPA asteroid (5247) Krylov.

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The Spin State of NPA Rotator (5247) Krylov

  • Lee, Hee-Jae;Durech, Josef;Kim, Myung-Jin;Moon, Hong-Kyu;Kim, Chun-Hwey;Park, Jintae;Kim, Dong-Heun;Roh, Dong-Goo;Choi, Young-Jun;Yim, Hong-Suh;the DEEP-South Team
    • The Bulletin of The Korean Astronomical Society
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    • v.42 no.2
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    • pp.50.1-50.1
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    • 2017
  • The Non-Principal Axis (NPA) rotators can be clues to spin evolutionary processes of asteroids because their excited spin states evolve due to either internal or external forces. The NPA rotation of (5247) Krylov was confirmed by Lee et al. (2017) based on KMTNet photometric observations during the 2016 apparition. We conducted follow-up observations in 2017 apparition using the 0.6-2.1m telescopes in the northern hemisphere to determine the spin state and shape model of this asteroid. We found that it is rotating in the Short Axis Mode (SAM) based on the determined rotation period ($P_{\psi}=374.6hr$) and precession period ($P_{\phi}=67.48hr$). The greatest and intermediate principal inertia moments are nearly the same as $I_b/I_c=0.94$, but the smallest principal inertia moments are nearly half that of the others, $I_a/I_c=0.43$. This ratio of principal inertia moments suggests that dynamically equivalent shape of this asteroid is close to that of a prolate ellipsoid. In this presentation, we will provide the physical model of (5247) Krylov to discuss its possible spin evolutionary processes that acted on its spin.

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Investigation on the monotonic behavior of the steel rack upright-beam column connection

  • Cao, Yan;Alyousef, Rayed;Jermsittiparsert, Kittisak;Ho, Lanh Si;Alaskar, Abdulaziz;Alabduljabbar, Hisham;Alrshoudi, Fahed;Mohamed, Abdeliazim Mustafa
    • Smart Structures and Systems
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    • v.26 no.1
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    • pp.103-115
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    • 2020
  • The cold-formed steel storage racks are extensively employed in various industries applications such as storing products in reliable places and storehouses before distribution to the market. Racking systems lose their stability under lateral loads, such as seismic actions due to the slenderness of elements and low ductility. This justifies a need for more investigation on methods to improve their behavior and increase their capacity to survive medium to severe loads. A standardized connection could be obtained through investigation on the moment resistance, value of original rotational stiffness, ductility, and failure mode of the connection. A total of six monotonic tests were carried out to determine the behavior of the connection of straight 2.0 mm, and 2.6 mm thickness connects to 5 lug end connectors. Then, the obtained results are benched mark as the original data. Furthermore, an extreme learning machine (ELM) technique has been employed to verify and predict both moment and rotation results. Out of 4 connections, increase the ultimate moment resistance of connection by 13% and 18% for 2.0 mm and 2.6 mm upright connection, respectively.

A Bifurcation Analysis of Space Structures by Using 3D Beam-Column Element Considering Finite Deformations and Bowing Effect (유한변형과 굽힘효과가 고려된 3차원 보-기둥요소에 의한 공간구조물의 분기좌굴해석)

  • Lee, Kyung-Soo;Han, Sang-Eul
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.22 no.4
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    • pp.307-314
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    • 2009
  • The present paper briefly describes the space frame element and the fundamental strategies in computational elastic bifurcation theory of geometrically nonlinear, single load parameter conservative elastic spatial structures. A method for large deformation(rotation) analysis of space frame is based on an eulerian formulation, which takes into consideration the effects of large joint translations and rotations with finite deformation(rotation). The local member force-deformation relationships are based on the beam-column approach, and the change in member chord lengths caused by axial strain and flexural bowing are taken into account. and the derived geometric stiffness matrix is unsymmetric because of the fact that finite rotations are not commutative under addition. To detect the singular point such as bifurcation point, an iterative pin-pointing algorithm is proposed. And the path switching mode for bifurcation path is based on the non-negative eigen-value and it's corresponding eigen-vector. Some numerical examples for bifurcation analysis are carried out for a plane frame, plane circular arch and space dome structures are described.

Differential CORDIC-based High-speed Phase Calculator for 3D Depth Image Extraction from TOF Sensor (TOF 센서용 3차원 깊이 영상 추출을 위한 차동 CORDIC 기반 고속 위상 연산기)

  • Koo, Jung-Youn;Shin, Kyung-Wook
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.18 no.3
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    • pp.643-650
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    • 2014
  • A hardware implementation of phase calculator for extracting 3D depth image from TOF(Time-Of-Flight) sensor is described. The designed phase calculator adopts redundant binary number systems and a pipelined architecture to improve throughput and speed. It performs arctangent operation using vectoring mode of DCORDIC(Differential COordinate Rotation DIgital Computer) algorithm. Fixed-point MATLAB simulations are carried out to determine the optimal bit-widths and number of iteration. The phase calculator has ben verified by FPGA-in-the-loop verification using MATLAB/Simulink. A test chip has been fabricated using a TSMC $0.18-{\mu}m$ CMOS process, and test results show that the chip functions correctly. It has 82,000 gates and the estimated throughput is 400 MS/s at 400Mhz@1.8V.