• Title/Summary/Keyword: Super Matrix

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Effect of R Phase Formation on the Mechanical Properties of 25Cr-7Ni-2Mo-4W Super Duplex Stainless Steel (25Cr-7Ni-2Mo-4W 슈퍼 2상 스테인리스강의 기계적 성질에 미치는 R상의 영향)

  • Lee, Byung-Chan;Kang, Chang-Yong
    • Korean Journal of Materials Research
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    • v.24 no.8
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    • pp.401-406
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    • 2014
  • In this study, we investigated the precipitation behavior of the R-phase precipitated at the initial stage of aging and its effects on the mechanical properties of 25%Cr-7%Ni-2%Mo-4%W super duplex stainless steel. The R-phase was mainly precipitated at the interface of ferrite/austenite phases and inside of the ferrite phase during the initial stage of aging. It was transformed into the ${\sigma}$-phase with an increase of the aging time. The ferrite phase was decomposed into a new austenite(${\gamma}_2$)phase and the ${\sigma}$-phase by an aging treatment. The R phase was an intermetallic compound showing higher molybdenum and tungsten concentrations than the matrix and also showed higher molybdenum and tungsten concentrations than the ${\sigma}$ phase. In the initial stage of aging, precipitation of the R-phase did not change the hardness, the strength and the elongation. The hardness and the strength increased upon a longer aging time, but the elongation rapidly decreased. These results show that the R-phase did not significantly affect the hardness and the strength, though it did influence the elongation.

The Design of the Feedback Control System of Electromagnetic Suspension Using Kalman Filter

  • Jo, Jeong-Min;Han, Young-Jae;Lee, Chang-Young
    • International Journal of Railway
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    • v.4 no.4
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    • pp.93-96
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    • 2011
  • The basic element of the EMS suspension is the electromagnet system, which suspends the vehicle without contact by attracting forces to the rails at the guideway. The suspension of a vehicle by attractive magnetic forces is inherently unstable and consequently it is continuously adjusted by the strength of the suspending electromagnet from rail irregularity and bending of the guideway. In order to improve reliable tracking, it needs to get feedback signals without measurement delay time. In this paper the concept of feedback control system with Kalman Filter in EMS is proposed. The input signals in the feedback control system are an air-gap and an acceleration signal. The air-gap signal with noise from the gap sensor is transformed to the filtered air-gap signal y without measurement delay time by using Kalman Filter. The filtered air-gap signal is transformed to a relative velocity and a relative acceleration signal. Then it multiplies these values by gain matrix in order to get the actuator's reference voltage value. The simulation results show that the dynamic responses of the suspension system can be improved by reducing the influence of measurement delay time of air-gap signals.

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Seismic Analysis of Flat Slab Structures considering Stiffness Degradation (강성저감을 고려한 플랫슬래브 구조물의 지진해석)

  • 김현수;이승재;이동근
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • 2003.09a
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    • pp.191-198
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    • 2003
  • Flat slab system has been adopted in many buildings constructed recently because of the advantage of reduced floor heights to meet the economical and architectural demands. Structural engineers commonly use the equivalent frame method(EFM) with equivalent beams proposed by Jacob S. Grossman in practical engineering for the analysis of flat slab structures. However, in many cases, when it is difficult to use the EFM, it is necessary to use a refined finite element model for an accurate analysis. But it would take significant amount of computational time and memory if the entire building structure were subdivided into a finer mesh. An efficient analytical method is proposed in this study to obtain accurate results in significantly reduced computational time. The proposed method employs super elements developed using the matrix condensation technique and fictitious beams are used in the development of super elements to enforce the compatibility at the interfaces of super elements. The stiffness degradation of flat slab system considered in the EFM was taken into account by reducing the elastic modulus of floor slabs in this study. Static and dynamic analyses of example structures were peformed and the efficiency and accuracy of the proposed method were verified by comparing the results with those of the refined finite element model and the EFM.

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Enhanced adhesion properties of conductive super-hydrophobic surfaces by using zirco-aluminate coupling agent

  • Park, Myung-Hyun;Ha, Ji-Hwan;Song, Hyeonjun;Bae, Joonwon;Park, Sung-Hoon
    • Journal of Industrial and Engineering Chemistry
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    • v.68
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    • pp.387-392
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    • 2018
  • Various technical approaches and concepts have been proposed to develop conductive super-hydrophobic (SH) surfaces. However, most of these approaches are not usable in practical applications because of insufficient adhesion and cost issues. Additionally, durability and uniformity issues are still in need of improvement. The goal of this research is to produce a large-area conductive SH surface with improved adhesion performance and uniformity. To this end, carbon nanotubes (CNT) with a high aspect ratio and elastomeric polymer were utilized as a conductive filler and matrix, respectively, to form a coating layer. Additionally, nanoscale silica particles were utilized for stable implementation of the conductive SH surface. To improve the adhesion properties between the SH coating layer and substrate, pretreatment of the substrate was conducted by utilizing both wet and dry etching processes to create specific organic functional groups on the substrate. Following pretreatment of the surface, a zirco-aluminate coupling agent was utilized to enhance adhesion properties between the substrate and the SH coating layer. Raman spectroscopy revealed that adhesion was greatly improved by the formation of a chemical bond between the substrate and the SH coating layer at an optimal coupling agent concentration. The developed conductive SH coating attained a high electromagnetic interference (EMI) shielding effectiveness, which is advantageous in self-cleaning EMI shielding applications.

Analysis of Shear Wall with Openings Using Super Element (슈퍼요소를 이용한 개구부를 가진 전단벽의 해석)

  • 이동근;김현수;남궁계홍
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2001.04a
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    • pp.343-350
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    • 2001
  • The box system, composed only of reinforced concrete walls and slabs, are adopted by many high-rise apartment buildings recently constructed in Korea. In the buildings, one or more relatively large openings are cut in a shear wall for functional reasons. The openings influence the internal stress of the shear wall and also the structural behavior. Therefore, it is necessary to use subdivided plate elements for accurate analysis of the box system with openings. But it would cost tremendous amount of analysis time and computer memory if the shear wall is subdivided into a finer mesh in the analysis of high-rise buildings. So, it is difficult to apply this modeling method to practical procedure. In this study, an efficient method is proposed for the efficient and accurate analysis of shear wall with openings. The proposed method used the super element and matrix condensations, fictitious beam technique.

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Efficient Floor Vibration Analysis in A Shear Wall Building Structure (벽식구조물의 효율적인 연직진동해석)

  • Kim, Hyun-Su;Lee, Dong-Guen
    • Journal of the Earthquake Engineering Society of Korea
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    • v.8 no.6 s.40
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    • pp.55-66
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    • 2004
  • Recently, many high-rise apartment buildings using the box system, composed of only reinforced concrete walls and slabs, have been constructed. In residential buildings such as apartments, vibrations occur from various sources and these vibrations transfer to neighboring residential units through walls and slabs. It is necessary to use a refined finite element model for an accurate vibration analysis of shear wall building structures. But it would take significant amount of computational time and memory if the entire building structure were subdivided into a finer mesh. Therefore, an efficient analytical method, which has only translational DOFs perpendicular to walls or slabs by the matrix condensation technique, is proposed in this study to obtain accurate results in significantly reduced computational time. If all of the DOFs except those perpendicular to walls or slabs in the shear wall structure eliminated using the matrix condensation technique at a time, the computational time for the matrix condensation would be significant. Thus, the modeling technique using super elements and substructuring technique is proposed to reduce the computational time for the matrix condensation. Dynamic analysis of 3-story and 5-story shear wall example structures were performed to verify the efficiency and accuracy of the proposed method. It was confirmed that the proposed method can provide the results with outstanding accuracy requiring significantly reduced computational time and memory.

Joint Time Delay and Angle Estimation Using the Matrix Pencil Method Based on Information Reconstruction Vector

  • Li, Haiwen;Ren, Xiukun;Bai, Ting;Zhang, Long
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.12 no.12
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    • pp.5860-5876
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    • 2018
  • A single snapshot data can only provide limited amount of information so that the rank of covariance matrix is not full, which is not adopted to complete the parameter estimation directly using the traditional super-resolution method. Aiming at solving the problem, a joint time delay and angle estimation using matrix pencil method based on information reconstruction vector for orthogonal frequency division multiplexing (OFDM) signal is proposed. Firstly, according to the channel frequency response vector of each array element, the algorithm reconstructs the vector data with delay and angle parameter information from both frequency and space dimensions. Then the enhanced data matrix for the extended array element is constructed, and the parameter vector of time delay and angle is estimated by the two-dimensional matrix pencil (2D MP) algorithm. Finally, the joint estimation of two-dimensional parameters is accomplished by the parameter pairing. The algorithm does not need a pseudo-spectral peak search, and the location of the target can be determined only by a single receiver, which can reduce the overhead of the positioning system. The theoretical analysis and simulation results show that the estimation accuracy of the proposed method in a single snapshot and low signal-to-noise ratio environment is much higher than that of Root Multiple Signal Classification algorithm (Root-MUSIC), and this method also achieves the higher estimation performance and efficiency with lower complexity cost compared to the one-dimensional matrix pencil algorithm.

Crystallization Mechanisms of Joule-Heating-Induced Crystallization

  • Park, Doo-Jung;Ro, Jae-Sang
    • Journal of Information Display
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    • v.10 no.2
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    • pp.76-79
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    • 2009
  • In Joule-heating-induced crystallization, solid-to-solid or liquid-to-solid phase transformation could occur. It was found that novel physical phenomena that randomly nucleated liquid seeds, followed by rapid solidification in an amorphous matrix, during the Joule-heating-up period play an important role especially in liquid-to-solid transformation. Under some processing conditions, super-grains sized 6-8 ${\um}m$ were produced by the lateral growth from the initial seeds, without any artificially control.

ERROR REDUCTION FOR HIGHER DERIVATIVES OF CHEBYSHEV COLLOCATION METHOD USING PRECONDITIONSING AND DOMAIN DECOMPOSITION

  • Darvishi, M.T.;Ghoreishi, F.
    • Journal of applied mathematics & informatics
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    • v.6 no.2
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    • pp.523-538
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    • 1999
  • A new preconditioning method is investigated to reduce the roundoff error in computing derivatives using Chebyshev col-location methods(CCM). Using this preconditioning causes ration of roundoff error of preconditioning method and CCm becomes small when N gets large. Also for accuracy enhancement of differentiation we use a domain decomposition approach. Error analysis shows that for this domain decomposition method error reduces proportional to the length of subintervals. Numerical results show that using domain decomposition and preconditioning simultaneously gives super accu-rate approximate values for first derivative of the function and good approximate values for moderately high derivatives.