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THE INVESTIGATION OF PSEUDOELASTIC NITI WIRES FOR DAMPING USES

  • Pan, Qiang;Cho, Chong-Du;Lu, Sheng
    • Proceedings of the KSME Conference
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    • 2007.05a
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    • pp.154-159
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    • 2007
  • Some shape memory alloys like NiTi show noticeable high damping property in pseudoelastic range. Due to its instinct characteristics, a NiTi alloy is commonly used for passive damping applications, in which the energy may be dissipated by the conversion from mechanical to thermal energy. Previous researches found the NiTi wires own higher damping property than the bars; therefore the wire form is adopted in this study. A loss factor is introduced for measuring the damping property of the NiTi wires. The experimental observation shows the mechanical behaviors of NiTi wires are dependent on temperature, strain rate and strain amplitude. Moreover, it is found the first several decades of loading-unloading cycles can obviously influence the property of NiTi wires under the same working conditions.

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An Effective Pedagogical Method for Nodal Analysis in Linear Circuit (선형회로에서 마디해석법의 효과적인 교수법)

  • Kim, Gwang Won;Hyun, Seung-Ho
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.27 no.7
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    • pp.76-81
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    • 2013
  • This paper presents an effective pedagogical method for nodal analysis in linear circuit. In the proposed method, basic equations are built only for passive elements and independent current sources. And then, the basic equations are modified by considering other sources such as voltage sources and dependent current sources. In the proposed method, the equations are presented in form of a matrix and a vector of which elements are built systematically by considering every element in a circuit one by one. This make the proposed method easy to apply to intricately composed circuit and easy to solve the final simultaneous equations and easy to realize as computer program for nodal analysis and easy to memorize compared to the conventional method.

Cyclic behavior of DCFP isolators with elliptical surfaces and different frictions

  • Abdollahzadeh, Gholamreza;Darvishi, Reza
    • Structural Engineering and Mechanics
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    • v.64 no.6
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    • pp.731-736
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    • 2017
  • Friction Pendulum isolators are tools developed in the past few decades. The simplest form of these isolators, are FPS whose main disadvantages are having a constant frequency independent of the frequency of the structure. For this reason, researchers have invented VFPI isolator whose frequency is variable and depends on displacement. Another friction pendulum isolator is DCFP isolator which is a combination of two FPS isolators. In this article, first by changing the geometry of DCFP isolator plates from spherical to elliptical, the motion and frequency equations of DVFPI isolators are defined, and then the seismic behavior of DVFPI isolators are analyzed in various geometric and plate friction settings using motion equations, and confirmed using ABAQUS software. The most important results of this study are that the hysteresis behavior of DVFPI isolators are severely nonlinear, its curve follows two distinct curvatures, and that the restoring force is faced with softening mechanism that limits the seismic force transmitted to the structure, whereas the restoring force in DCFP isolators increases linearly with increasing displacement.

Secrecy Outage Probability of AF Relay Transmission with MRC/TAS in Presence of Eavesdropper

  • Hwang, Kyu-Sung
    • Journal of Korea Multimedia Society
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    • v.19 no.3
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    • pp.620-625
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    • 2016
  • In this paper, we offer the secrecy outage probability of the amplify-and-forward (AF) transmission, which consists of one source, one destination, one relay, and one passive eavesdropper. Particularly, we consider that the relay is equipped with multiple antennas while other terminals is utilized with single antenna and apply diversity techniques (for both the reception and the transmission) at the relay to achieve gains in a secrecy outage performance. Additionally, we analyze the exact secrecy outage probability of the proposed systems in a one-integral form. Finally, some numerical examples are given to verify our provided analytical results for different system conditions.

Design and fabrication of MMIC VCO for double conversion TV tuner (이중 변환 TV 튜너용 MMIC 전압제어발진기의 설계 제작)

  • 황인갑;양전욱;박철순;박형무;김학선;윤경식
    • Journal of the Korean Institute of Telematics and Electronics A
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    • v.33A no.7
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    • pp.121-126
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    • 1996
  • In this paper an MMIC VCO which can be used in a double conversion TV tuner is designed, fabricated and measured. The VCO is designed using the small signal method and fabricated using ETRI GaAs MMIC foundry. The 3x200μm gate width MESFET with 1μm gate length is used for an active device and MIM capacitors, spiral inductors, thin film resitors are used as passive elements. The VCO has output power of 10.95dBm at 1955 MHz with 5V bias voltage and 4V tuning voltage. The oscillation frequency change form 1947 MHz to 1964 MHz is obtaine dby an external varactor diode connected to the gate with a tuning voltage from 0 V to 6V.

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A 300MHz CMOS phase-locked loop with improved pull-in process (루프인식 속도를 개선한 300MHz PLL의 설계 및 제작)

  • 이덕민;정민수;김보은;최동명;김수원
    • Journal of the Korean Institute of Telematics and Electronics A
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    • v.33A no.10
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    • pp.115-122
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    • 1996
  • A 300MHz PLL including FVC (frequency to voltage converter) is designed and fabricated in 0.8μm CMOS process. In this design, a FVC and a 2nd - order passive filter are added to the conventional charge-pump PLL to improve the acquisition time. The dual-rijng VCO(voltage controlled oscillator) realized in this paper has a frequency range form 208 to 320MHz. Integrated circuits have been fully tested and analyzed in detail and it is proved that pull-in speed is enhanced with the use fo FVC. In VCO range from 230MHz to 310MHz, experimental results show that realized PLL exhibits 4 times faster pull-in speed than that of conventional PLL.

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Streetwalkers: Phantom Monuments of the Post-Apartheid City ((거리의) 창부들: 흑인격리정책 폐지 후 도시의 환영적 기념물)

  • Maltz-Leca, Leora
    • The Journal of Art Theory & Practice
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    • no.10
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    • pp.63-84
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    • 2010
  • This essay examines how the figure of Liberty has been refashioned in the streets of post-apartheid South Africa, addressing three public art works installed in Johannesburg over the past decade: Reshada Crouse's oil painting Passive Resistance, Marlene Dumas' tapestry The Benefit of the Doubt and William Kentridge's and Gerhard Marx's sculpture Firewalker. Even as these monumental works all reprise Delacroix's Liberty on the Barricades-an icon of the city street and its revolutionary barricades-so too this trio of Liberties have become mere phantoms of their vaunted archetype. Haunted specters, they quarrel with the mythologized chimera of Liberty, taking issue with the fraught tradition of pinning regime change onto the body of the female nude. Drawing instead on South African histories of women's resistance, in which female nudity has been repeatedly marshaled as a form of dissent, the Liberties circling Johannesburg hybridize their European template with local traditions of female political opposition to colonial and postcolonial male authority.

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Effect of Acid Fog on Rust Formation and Fatigue Strength of Weathering Steel (산성안개가 내후성강재의 녹형성 및 피로강도에 미치는 영향)

  • Kim, Min-Gun;Ku, Eun-hoi
    • Journal of Industrial Technology
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    • v.22 no.B
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    • pp.13-20
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    • 2002
  • The purpose of this study is to investigate the effect of acid fog on the rust formation behavior of weathering steel (SMA50) which is used in uncoated bridges. Weathering steel didn't form the passive film under the environment of acid fog(pH5,6), whereas the environment of distilled water formed the protective oxide film. Therefore, the construction of weathering steel under the environment extremely exposed to SOx and NOx which are the main compositions of acid fog is not adequate. Fatigue limits of weathering steel under acid fog environment are remarkably decreased as compared with environment of distilled water. The corrosive constituents in acid fog has piled up the corrosion products on specimen surface and generated the corrosion pits. Because of the high stress concentration arising at this corrosion pit, relatively low fatigue limits were obtained for acid fog specimens.

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Corrosion of Titanium Alloys in High Temperature Seawater

  • Pang, J.J.;Blackwood, D.J.
    • Corrosion Science and Technology
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    • v.14 no.4
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    • pp.195-199
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    • 2015
  • Materials of choice for offshore structures and the marine industry have been increasingly favoring materials that offer high strength-to-weight ratios. One of the most promising families of light-weight materials is titanium alloys, but these do have two potential Achilles' heels: (i) the passive film may not form or may be unstable in low oxygen environments, leading to rapid corrosion; and (ii) titanium is a strong hydride former, making it vulnerable to hydrogen embrittlement (cracking) at high temperatures in low oxygen environments. Unfortunately, such environments exist at deep sea well-heads; temperatures can exceed 120C, and oxygen levels can drop below 1 ppm. The present study demonstrates the results of investigations into the corrosion behavior of a range of titanium alloys, including newly developed alloys containing rare earth additions for refined microstructure and added strength, in artificial seawater over the temperature range of 25C to 200C. Tests include potentiodynamic polarization, crevice corrosion, and U-bend stress corrosion cracking.

Development of Balancer for Reduced Vibration of Washing Machine (세탁기의 진동 감소를 위한 밸런서 개발)

  • 폴위즈바;웨이지아카오;박정수;김형균
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1997.04a
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    • pp.602-607
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    • 1997
  • Ball balance belong to a kind of automatic balancers opten referred to as direct balancer or passive mass systems. In such systems the balancing is achieved with free masses. One of the most prevalent problems encountered in washing is the vibration during spin cycle. The primary cause of this vibration is mass unbalance associated with non unform distribution of clothes. Front loading type machine of European style, especially, has inherent unbalance mass due to its shape and this then makes the vibration worse than top loading type machine, which is more popular in Korea. Since the mass distribution of cloths is random and can not be predicted in advance, direct automatic balances appear to be the only feasible alternative. The results form computer simulation and experimental testing will be presented together with stability implications.

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