• Title/Summary/Keyword: Separation control

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Non-contact type AFM using frequency separation scheme (주파수응답 분리방법을 이용한 비접촉식 AFM)

  • 이성규;염우섭;박기환;송기봉;김준호;김은경;박강호
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2002.10a
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    • pp.375-378
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    • 2002
  • In this paper, the frequency response separation scheme is proposed for high scanning speed and simple structure of non-contact type of AFM. A self-sensing cantilever is attached on the actuator for detect the atomic force between tip and the media surface. VCM or PZT are used for actuator. This paper presents the method to simplify the actuator structure and the performance of each actuator for non-contact type AFM. Based on the frequency response separation scheme, the only one actuator plays roles 1311owing low frequency surface and modulating self-sensing cantilever tip in contrast with convention non-contact type AFM. 10 ${\mu}{\textrm}{m}$ standard grid sample imaged to verify proposed scheme. This result shows the possibility simplifying the actuator structure and reducing cost of non-contact type AFM.

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Numerical Analysis of Relative Orbit Control Strategy for CANYVAL-X Mission

  • Lee, Youngro;Park, Sang-Young;Park, Jae-Pil;Song, Youngbum
    • Journal of Astronomy and Space Sciences
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    • v.36 no.4
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    • pp.235-248
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    • 2019
  • This paper suggests a relative orbit control strategy for the CubeSat Astronomy by NASA and Yonsei using Virtual Telescope Alignment eXperiment (CANYVAL-X) mission whose main goal is to demonstrate an essential technique, which is an arrangement among two satellites and a specific celestial object, referred to as inertial alignment, for a next-generation virtual space telescope. The inertial alignment system is a relative orbit control system and has requirements for the relative state. Through the proposed orbit control strategy, consisting of separation, proximity keeping, and reconfiguration, the requirements will be satisfied. The separation direction of the two CubeSats with respect to the orbital plane is decided to provide advantageous initial condition to the orbit controller. Proximity keeping is accomplished by differential atmospheric drag control (DADC), which generates acceleration by changing the spacecraft's effective cross section via attitude control rather than consuming propellant. Reconfiguration is performed to meet the requirements after proximity keeping. Numerical simulations show that the requirements can be satisfied by the relative orbit control strategy. Furthermore, through numerical simulations, it is demonstrated that the inertial alignment can be achieved. A beacon signal had been received for several months after the launch; however, we have lost the signal at present.

Implementation and Evaluation of Dynamic and Distributed Mapping System in ID-LOC Separation Internet Architecture (ID-LOC 분리 기반 인터넷 구조에서 분산형 매핑 시스템의 구현 및 평가)

  • Kang, Hyung-Woo;Choi, Nak-Jung;Kim, Ji-In;Jung, Heeyoung;Koh, Seck-Joo
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.37B no.11
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    • pp.984-992
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    • 2012
  • In this paper, we discuss a new architecture of future Internet for mobile-oriented environments, named Mobile-Oriented Future Internet (MOFI). The MOFI architecture is designed with Host Identifier and Local Locator (HILL) for identifier and locator separation. Based on the HILL separation architecture, we propose a Dynamic and Distributed Mapping System (DDMS) for identifier-locator mapping control. In DDMS, the mapping control function is distributed onto each access router in the domain, which is different from the centralized approach using a central anchor. For validation of the proposed MOFI-DDMS architecture, we implemented the data delivery and mapping control functions using Linux platform. From the testbed experimental results, we see that the DDMS architecture can give better performance than the existing Proxy Mobile IP (PMIP) protocol in terms of data transmission throughput.

Effect of internal stress on cyclic fatigue failure in .06 taper ProFile (내부 응력이 .06 taper ProFile의 피로 파절에 미치는 영향)

  • Jung, Hye-Rim;Kim, Jin-Woo;Cho, Kyung-Mo;Park, Se-Hee
    • Restorative Dentistry and Endodontics
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    • v.37 no.2
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    • pp.79-83
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    • 2012
  • Objectives: The purpose of this study was to evaluate the relation between intentionally induced internal stress and cyclic fatigue failure of .06 taper ProFile. Materials and Methods: Length 25 mm, .06 taper ProFile (Dentsply Maillefer), and size 20, 25, 30, 35 and 40 were used in this study. To give the internal stress, the rotary NiTi files were put into the .02 taper, Endo-Training-Bloc (Dentsply Maillefer) until auto-stop by torque controlled motor. Rotary NiTi files were grouped by the number of induced internal stress and randomly distributed among one control group and three experimental groups (n = 10, Stress 0 [control], Stress 1, Stress 2 and Stress 3). For cyclic fatigue measurement, time for separation of the rotary NiTi files was recorded. The fractured surfaces were observed by field emission scanning electron microscope (FE-SEM, SU-70, Hitachi). The time for separation was statistically analyzed using two-way ANOVA and post-hoc Scheffe test at 95% level. Results: In .06 taper ProFile size 20, 25, 30, 35 and 40, there were statistically significant difference on time for separation between control group and the other groups (p < 0.05). Conclusion: In the limitation of this study, cyclic fatigue failure of .06 taper ProFile is influenced by internal stress accumulated in the files.

Manufacturing and Application of Activated Carbon and Carbon Molecular Sieves in Gas Adsorption and Separation Processes (가스 흡착 및 분리공정용 활성탄소와 탄소분자체의 제조 및 응용)

  • Jeong, Seo Gyeong;Ha, Seongmin;Lee, Young-Seak
    • Applied Chemistry for Engineering
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    • v.33 no.5
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    • pp.488-495
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    • 2022
  • Activated carbon (AC) and carbon molecular sieve (CMS) have attracted attention as porous materials for recovery and separation of greenhouse gases. The carbon molecular sieve having uniform pores is used for collecting and separating gases because it may selectively adsorb a specific gas. The size and uniformity of pores determine the performance of the CMS, and chemical vapor deposition (CVD) is widely used to coat the surface with a predetermined thickness in order to control the CMS's micropores. This CVD method can be used to control the size of pores in CMS manufacturing, but it must be optimized because of its various experimental variables. Therefore, in order to produce AC and CMS for gas adsorption and separation, this review focuses on various activation processes and pore control technologies by CVD and surface treatment.

Active control of flow over a sphere using electro-magnetic actuators (전자석 액츄에이터를 이용한 구 주위의 유동제어)

  • Park, Jin-Il;Choi, Hae-Cheon;Jeon, Woo-Pyung
    • Proceedings of the KSME Conference
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    • 2000.04b
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    • pp.497-501
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    • 2000
  • Flow over a sphere is controlled experimentally at $Re=10^5$ using electro-magnetic actuators. The electro-magnetic actuator developed in this study is composed of the permanent magnet electro-magnet membrane and slot. Eight actuators are placed inside the sphere at equally spaced intervals on a latitudinal plane and the position of the control slot is 76 from the stagnation point. Each actuator generates a periodic blowing and suction through the slot at variable frequencies of $10{\sim}140Hz$ and variable amplitudes by controlling electric signals applied to the electro-magnet. Drag on the sphere measured using a load cell is significantly reduced with control at the forcing frequencies larger than the natural shedding frequency $({\approx}14Hz\;at\;Re=10^5)$, whereas drag is slightly increased at the forcing frequency of 10Hz. It is shown from pressure measurement that the static pressure in the rear surface of the sphere is significantly increased with control, indicating that the separation is delayed due to control. Flow visualizations also show that the detaching shear layer is more attracted to the sphere center with control, the separation bubble size is significantly reduced, and motion inside the bubble is very weak, as compared to the case of uncontrolled flow.

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Hybrid Sensor-less Control of Permanent Magnet Synchronous Motor in Low-speed Region

  • Yamamoto, Yasuhiro;Funato, Hirohito;Ogasawara, Satoshi
    • Journal of Power Electronics
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    • v.8 no.4
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    • pp.301-308
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    • 2008
  • This paper proposes a method of improving the stability in sensor-less control of permanent magnet synchronous motors. The control method for low-speed region is divided into two: One is a high frequency method, which involves a problem of reverse rotation once misdetection of the permanent magnet polarity should occur, and another one is a current drive method, which has a problem that phase and speed oscillations are caused by quick speed changes. Hence, authors propose adoption of the current drive method for the basic control system with added compensation of stabilization by means of the high frequency method. This combination secures stable control with no risk of reversal and less vibration. In addition, authors have also considered a frequency separation filter of a shorter delay time so that current control performance will not lower even when high frequencies are introduced. This filter has achieved simplified compensation using repetitive characteristic through the utilization of the periodicity of high frequency current. Simulation and experiment have been conducted to verify that the stable performance of this system is improved.

Observer-Based Output-feedback Sampled-Data Controlling the Singularly Perturbed Takagi-Sugeno Fuzzy Model (특이섭동 타카기 수게노 퍼지모델의 관측기기반 - 출력궤환 샘플치제어)

  • Kang, Hyoung Bin;Moon, Ji Hyun;Lee, Ho Jae
    • Journal of Institute of Control, Robotics and Systems
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    • v.22 no.9
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    • pp.679-685
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    • 2016
  • This paper addresses an observer-based output-feedback sampled-data controller design problem for nonlinear systems in Takagi-Sugeno (T-S) form including singular perturbations. The design condition is represented in terms of linear matrix inequalities. The separation principle is also investigated.

Separating VNF and Network Control for Hardware-Acceleration of SDN/NFV Architecture

  • Duan, Tong;Lan, Julong;Hu, Yuxiang;Sun, Penghao
    • ETRI Journal
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    • v.39 no.4
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    • pp.525-534
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    • 2017
  • A hardware-acceleration architecture that separates virtual network functions (VNFs) and network control (called HSN) is proposed to solve the mismatch between the simple flow steering requirements and strong packet processing abilities of software-defined networking (SDN) forwarding elements (FEs) in SDN/network function virtualization (NFV) architecture, while improving the efficiency of NFV infrastructure and the performance of network-intensive functions. HSN makes full use of FEs and accelerates VNFs through two mechanisms: (1) separation of traffic steering and packet processing in the FEs; (2) separation of SDN and NFV control in the FEs. Our HSN prototype, built on NetFPGA-10G, demonstrates that the processing performance can be greatly improved with only a small modification of the traditional SDN/NFV architecture.

A Study on the Flow Characteristics around a Coanda Control Surface

  • Hong, Seok-Jin;Lee, Seung-Hee
    • Journal of Ship and Ocean Technology
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    • v.8 no.2
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    • pp.13-19
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    • 2004
  • Jet flows applied tangential to a foil surface near the leading and/or trailing edges increase the lift of the foil by delaying the separation also known as the Coanda effects. Many experimental and numerical studies have proven the effectiveness of Coanda effects on circulation control and the effects have been found to be useful in practical application in many aerodynamics fields. Most of the previous works have studied the effects of the jet blowing near the trailing edges and investigated the influence of jet momentum on lift. A few experimental studies, however, focused on the separation bubble that develops near the leading edge and applied jet flow the edge to remove the bubble but only to find decrease in lift. In the present paper, a Coanda foil of 20% thickness ellipse with modified rounded leading and trailing edges was investigated, and the flow around the foil was numerically studied. The blowing around the leading edge only decreased the lift, as the experiments showed, but the suction considerably increased the lift.