• Title, Summary, Keyword: SMA

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From SMA to w-SMA

  • Hirano, Naomi;SMA team
    • The Bulletin of The Korean Astronomical Society
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    • v.42 no.2
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    • pp.59.2-59.2
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    • 2017
  • The Submillimeter Array (SMA) has provided forefront capabilities for high spatial and spectral resolution observations at submillimeter wavelengths from its excellent site on Mauna Kea, Hawaii since 2004. The SMA has continuously enhanced its capability. It is now equipped with two receivers in the 1.3 mm band (Rx230/Rx240) and two in the 0.85 mm band (Rx345/Rx400). The total bandwidth available is 8+8 GHz (per receiver) in the dual band or polarization mode. To maintain a leading role in the ALMA era, the SMA project is now upgrading its receivers, IF signal transport and correlator system. The new wideband SMA - the wSMA - will provide the instantaneous coverage of 56 GHz. In this presentation, I will introduce the latest status of the SMA, upgrade plan to the w-SMA, the possible science cases with the w-SMA, and the roles of the w-SMA in the ALMA era.

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Preparation of High Range Water Reducer Containing Carboxylic Acid and Their Cement Absorptivity(I) (카르본산계 고성능감수제의 제조 및 그들의 시멘트 흡착성(I))

  • 김화중;강인규;김성훈;김우성;권영도
    • Magazine of the Korea Concrete Institute
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    • v.7 no.2
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    • pp.175-182
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    • 1995
  • Styrene-Maleic anhydride copolymer (SMA) was prepared by the radical copolmerization of styrene and maleic anhydride using ${\alpha}-{\alpha}'$ azobis(isobutyronitrile) as an initiatrr. SMA was further reacted with m-amino phenol to obtain aminophenol-substituted SMR (mSMA). Sulfonated SMA and mSMA were also prepared by the reaction of copolymers with sulfuric acid The copolyniers were characterized by infrared spectroscopy. It was found from the results of elemental analysis that the substitution degree of aminophenol in the mSMR is 44% and the degree is lowered to 35% after sulfonation. The percentage of copolymers adsorbed on the surface of cement particles was increased with a decrease of added copolymers. While, the arnourit of sulfonated SMA absorbed on the surface of cement particles was larger than that of the sulfonated mSMA The copolymers synthesized in this study are probably expected as a high range water reducer for coiicxte.

Effect of SMA on the Interfacial Shear Strength for Single Glass Fiber and PC/SAN Blends (SMA가 PC/SAN 블렌드와 유리섬유간의 계면결합력에 미치는 영향)

  • Lee, Ui-Hwan;Nam, Gi-Jun;Lee, Jae-Uk
    • Polymer(Korea)
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    • v.25 no.4
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    • pp.512-520
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    • 2001
  • One of the most important factors which affect the mechanical properties of fiber-reinforced composite materials is the interfacial shear strength (IFSS). The IFSS of glass fiber and polycarbonate (PC)/styrene-co-acrylonitrile (SAN) blend system has been measured by the single fiber fragmentation test (SFFT). SAN contents were varied up to 30 wt% and the IFSS increased with the SAN contents. Styrene-co-maleic anhydride (SMA) was used as the compatibilizer and the glass fiber was surface treated with organosilane coupling agents. Addition of small amount of SMA in PC/SAN blend improved the IFSS by chemical bonding between maleic anhydride and silanol. The optimum MA content was 0.4 wt% of total matrix contents. Also, IFSS was greatly affected by the miscibility condition of SAN/SMA blends, which depended on the copolymer composition of SAN and SMA. It was found out that, higher IFSS could be obtained when the SAN/SMA blend was in miscible pairs. In case of SAN/SMA miscible pairs, the IFSS depended on the MA content in total matrix, not on the MA content in SMA.

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Evaluation of Rutting and Deformation Strength Properties of Polymer Modified SMA Mixtures (개질재 첨가에 따른 SMA 혼합물의 소성변형 및 변형강도 특성 연구)

  • Kim, Hyun-H.;Choi, Young-R.;Kim, Kwang-W.;Doh, Young-S.
    • International Journal of Highway Engineering
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    • v.11 no.4
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    • pp.25-31
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    • 2009
  • In general, it is well known fact that the stone mastic asphalt (SMA) pavement has a high resistance against rutting. However, performance of SMA is not well measured by general method used in the laboratory. The objective of this study is to investigate an applicability of deformation strength ($S_D$) for performance estimation of SMA, and to find out the correlation between rut depth and dynamic stability, and $S_D$ of SMA. This study carried out wheel tracking test and Kim-test with optimum asphalt content (OAC) determined by mix design. The results indicated that the $S_D$ of SMA was very poorer than those of dense-graded asphalt mixtures. $S_D$ showed similar WT dynamic stability and rut-depth level. It was found that Kim-test was not reflected higher rutting resistance of SMA like as indirect tensile strength (ITS) test and Marshall stability test. Also, it was revealed that dynamic stability and rut-depth of WT had some problems to estimate rutting resistance of SMA mixtures.

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Experimental Test and Numerical Simulation on the SMA Characteristics and Behaviors through the Load-Training (하중 트레이닝을 통한 형상기억합금의 특성 실험과 거동 전산 모사)

  • Kim, Sang-Haun;Cho, Maeng-Hyo
    • Proceedings of the KSME Conference
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    • pp.700-705
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    • 2007
  • In this study, we observe the application of shape memory alloy(SMA) into smart structures for repeatable actuation, because SMA changes its material properties and characteristics progressively under cyclic loading conditions and finally reaches stable path(state) after a certain number of stress/temperature loading-unloading cycles, so called 'training'. In this paper, SMA wires that have been in a stable state through the training are used. Stress-strain curve of the SMA wire at different temperature levels are measured. In addition, we observe other important effects such as the rate effect according to strain rates for rapid actuation response. The current work presents the experimental test using SMA wire after training completion by mechanical cycling. Through these tests, we measure the characteristics of SMA. With the estimated SMA properties and effects, we compare the experimental results with the simulation results based on the SMA constitutive equations.

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Experimental Test and Numerical Simulation on the SMA Characteristics and Behaviors for Repeated Actuations (반복적인 작동을 위한 형상기억합금의 특성 실험과 거동 전산 모사)

  • Kim, Sang-Haun;Cho, Maeng-Hyo
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.31 no.3
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    • pp.373-379
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    • 2007
  • In this study, we observe the application of shape memory alloy(SMA) into smart structures for repeatable actuation, because SMA changes its material properties and characteristics progressively under cyclic loading conditions and finally reaches stable path(state) after a certain number of stress/temperature loading-unloading cycles, so called 'training'. In this paper, SMA wires that have been in a stable state through the training are used. Stress-strain curve of the SMA wire at different temperature levels are measured. In addition, we observe other important effects such as the rate effect according to strain rates for rapid actuation response. The current work presents the experimental test using SMA wire after training completion by mechanical cycling. Through these tests, we measure the characteristics of SMA. With the estimated SMA properties and effects, we compare the experimental results with the simulation results based on the SMA constitutive equations.

Use of SMA bars to enhance the seismic performance of SMA braced RC frames

  • Meshaly, Mohamed E.;Youssef, Maged A.;Abou Elfath, Hamdy M.
    • Earthquakes and Structures
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    • v.6 no.3
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    • pp.267-280
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    • 2014
  • Shape Memory Alloy (SMA) braces can be used to reduce seismic residual deformations observed in steel braced Reinforced Concrete (RC) frames. To further enhance the seismic performance of these frames, the use of SMA bars to reinforce their beams is investigated in this paper. Three-story and nine-story SMA-braced RC frames are designed utilizing regular steel reinforcing bars. Their seismic performance is examined using twenty seismic ground motions. The frames are then re-designed using SMA reinforcing bars. Different design alternatives representing different locations for the SMA reinforcing bars are considered. The optimum locations for the SMA bars are identified after analysing the design alternatives. The seismic performance of these frames has indicated better deformability when SMA bars are used in the beams.

Position estimation and control of SMA actuators based on electrical resistance measurement

  • Song, Gangbing;Ma, Ning;Lee, Ho-Jun
    • Smart Structures and Systems
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    • v.3 no.2
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    • pp.189-200
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    • 2007
  • As a functional material, shape memory alloy (SMA) has attracted much attention and research effort to explore its unique properties and its applications in the past few decades. Some of its properties, in particular the electrical resistance (ER) based self-sensing property of SMA, have not been fully studied. Electrical resistance of an SMA wire varies during its phase transformation. This variation is an inherent property of the SMA wire, although it is highly nonlinear with hysteresis. The relationship between the displacement and the electrical resistance of an SMA wire is deterministic and repeatable to some degree, therefore enabling the self-sensing ability of the SMA. The potential of this self-sensing ability has not received sufficient exploration so far, and even the previous studies in literature lack generality. This paper concerns the utilization of the self-sensing property of a spring-biased Nickel-Titanium (Nitinol) SMA actuator for two applications: ER feedback position control of an SMA actuator without a position sensor, and estimation of the opening of a SMA actuated valve. The use of the self-sensing property eliminates the need for a position sensor, therefore reducing the cost and size of an SMA actuator assembly. Two experimental apparatuses are fabricated to facilitate the two proposed applications, respectively. Based on open-loop testing results, the curve fitting technique is used to represent the nonlinear relationships between the displacement and the electrical resistance of the two SMA wire actuators. Using the mathematical models of the two SMA actuators, respectively, a proportional plus derivative controller is designed for control of the SMA wire actuator using only electrical resistance feedback. Consequently, the opening of the SMA actuated valve can be estimated without using an extra sensor.

The Bending and Twisting Analysis of SMA/Composite Beams (SMA 선이 삽입된 복합재 보의 굽힘 및 비틀림 해석)

  • Park, Bum-Sik;Kim, Cheol
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.151-154
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    • 2001
  • Shape memory alloy (SMA) has demonstrated its potentials for various smart structure applications. SMA wires undergo a reversible phase transformation from martensite to austenite as temperature increases. This transformation leads to shape recovery and associated recovery strains. If SMA actuators are embedded off the neutral surface and are oriented in arbitrary angles with respect to a beam axis, then the beam bends and twists due to the coupling effects of recovery strains activated. In this study, the bending and twisting of a SMA/Composite beam were controlled by both electric resistive heating and passive elastic tailoring. 3-dimensional finite element formulations were derived and validated to analyze the responses of the SMA/Composite beam. Numerical results show that the shape of the SMA/Composite beam can be controlled by judicious choices of control temperatures, SMA angles, and elastic tailoring.

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